South Korea: SIP providers and connecting a number to the PBX

This page continues the general guide to connecting a provider's number to the PBX: that page covers everything that is the same in any country — the two trunk modes, what to ask the operator, what to enter in the form, network and compatibility and checking the connection. Here are the Korean specifics: who in the country will actually sell you a number with a trunk, what to enter in the form, and which contract terms to check in advance.

The data was collected on 10 September 2026 from operator websites, their documentation and regulator documents; links are in the "Sources" section.

In brief#

• A dedicated PBX is created for Korean locations. A telecom licence is required from whoever sells the number — the venue only needs a contract with a licensed Korean operator.
• ⚠️⚠️ The market splits into "the big three" and everyone else. KT, SK Broadband and LG U+ sell internet telephony as a service with their own equipment on the customer's premises (KT bundles «구내 교환장비 무상임대» — an IP PBX leased free of charge; LG U+ offers 교환기구축형 DCS). They do not publish SIP trunk parameters and, as a rule, do not give them to subscribers, so there is nothing to enter into a cloud PBX.
• Where to start. ClawOps (클로옵스) is a Korean service launched in 2026 with fully documented trunking to a third-party PBX: a 070 number is issued in minutes, inbound calls are delivered straight to our PBX's IP address, and outbound calls use an issued username and password. Wyz070 (삼성 와이즈070) by Samsung SDS is an established operator whose IP-LINK Digital product is explicitly designed for the customer's own IP PBX, and whose SIP server addresses have long been publicly known.
• ⚠️ The main local pitfall is the contract, not the technology. Operator terms require a subscriber with their own PBX not to expose it directly to the internet, to keep an administrator password of at least 8 characters changed every six months, and to install updates; all liability for a breach stays with the PBX owner. Our PBX is precisely "a PBX with a public address", so ask the operator for IP authentication with an allowlist and put your security measures in writing.
• ⚠️ The outgoing number is audited daily. The operator must maintain the range of valid numbers for a subscriber and compare outgoing calls against it at least once a day; a mismatch means blocked calls and a three-month suspension of service. In Korea, fill the “Show as” field only with a number registered with the same operator — or better, leave it empty.
• ⚠️ Paperwork. Both local operators (business registration certificate, corporate verification, lines capped by headcount) and international marketplaces come down to a Korean legal entity. Without one, a number is practically unobtainable.

Numbers in South Korea#

• Country code +82, national prefix 0, dropped in international format: 02-1234-5678 = +82 2 1234 5678.
• Landline numbers — an area code plus 7–8 subscriber digits: 02 Seoul, 031 Gyeonggi, 032 Incheon, 033 Gangwon, 041/042/043/044 Chungcheong, Daejeon and Sejong, 051–055 Busan, Ulsan, Daegu and Gyeongsang, 061–064 Jeolla and Jeju.
• Mobile numbers — 010 plus 8 digits (a single prefix since 2004; 011 and 016–019 remain with legacy subscribers).
• 070 plus 8 digits is internet telephony, 11 digits in total: 070-XXXX-XXXX. The second block is allocated between operators, so "070-4…" and "070-8…" belong to different companies. These are the numbers that trunk providers issue.
• Service ranges: 050 — personal numbers with forwarding, 060 — premium information lines, 080 — toll-free for the caller, 15XX / 16XX / 18XX — nationwide representative numbers (4 + 4 digits).
• Emergency services: 112 (police), 119 (fire and ambulance), 122 (coast guard).
• In “Lines” enter the number exactly as the provider issued it: the PBX matches the last seven digits, so writing it with +82 or with a leading 0 makes no difference. Providers deliver the number in national format without a plus sign: ClawOps uses 07012341234, and with Wyz070 the line name is the number itself, 07011112222. The big three do not publish their format — ask the account manager during provisioning.
• ⚠️ The seven-digit trap. 070-1234-5678 and the Seoul number 02-1234-5678 produce the same tail 2345678. If the venue has both a landline and a 070 number, the routing lines will merge — check this when you add the second line.

Who issues a number with a SIP trunk#

ClawOps — the only trunk with public documentation#

A Korean voice-flow and telephony service launched in 2026 in the AWS Seoul region. It fills a gap that Korea did not cover: local operators only provision trunks manually and by contract, while Twilio does not offer 070 numbers at all. Alongside its own voice flows, ClawOps publishes a complete third-party PBX contour: our PBX address as the inbound target, a separate credential for outbound calls, and an address allowlist.

How to get it: sign up in the console → obtain an API key → enable the "SIP 트렁크" add-on → issue a number. Numbers come from a pool — you cannot choose the code or the tail, and candidates are not shown before issuance. Companies must pass corporate verification. Pricing including tax: a 3-day free trial, Individual ₩19,000/month (1 concurrent call, 1 number, 100 outbound minutes), Business ₩99,000/month (10 calls, 10 numbers, 1,000 minutes); beyond the plan a number costs ₩1,000, an inbound minute ₩4 and an outbound minute ₩60.

How this maps onto our modes: inbound calls are delivered by ClawOps itself, dialling the sip:host[:port] address you configure on their side — that is IP authentication, no registration needed. Outbound calls use a digest credential whose realm is generated automatically from your account identifier.

What to enter in the admin panel (Telephony → "Trunks and connections" → “Add provider”):

What to configure on the provider's side: enable the "SIP 트렁크" add-on → create a SIP endpoint ("head office trunk") → add a route sip:<public IP of our PBX>:5060 with transport udp → create an IP allowlist and attach the SIP credential to it → switch the issued number to SIP routing pointing at that endpoint → hand over the “Static IP” from the "Server" tab → confirm in writing the G.711 a-law/µ-law codecs and the DTMF mode.

Pitfalls ⚠️

• There is no TCP in the route at all, and tls is something we cannot do — the route must be udp.
• Codecs and DTMF are not documented. We only support G.711 a-law, G.711 µ-law and G.722, and voice-menu digits are expected as separate RFC 2833 packets — agree both points in writing before you pay.
• The outgoing number is strictly limited to the account's own numbers: a foreign number in the From header is rejected with an error. The "Show as" field with an outside number will not work, technically or legally.
• You cannot pick the number — the venue gets a random 070.
• Representative 15XX/18XX numbers cannot be routed to our PBX: only forwarding is available for them. A memorable single number can be forwarded to your own 070, with the trunk living on the 070.
• The credential password cannot be recovered — if it is lost, issue a new credential and disable the old one.

Sources: creating a SIP endpoint · route to an external PBX · issuing a SIP credential · numbers · pricing — 10.09.2026.

Wyz070 (삼성 와이즈070) — the operator with known SIP domains#

An internet telephony operator run by Samsung SDS (support centre 1661-3311). It is the only one in the country whose SIP server addresses have long been publicly known — which is exactly why it gets picked when a line has to be plugged into a third-party PBX or softphone.

There are two products: IP-CENTREX — the operator's cloud PBX with their phones only, and IP-LINK — "using internet telephony on your existing switching equipment". We need IP-LINK Digital: its description explicitly allows for "installing a separate IP PBX". Ordering goes through the sales department or official dealers, the contract is corporate, and the number of lines is capped by the company's headcount.

The parameters below come from a published walkthrough of a working softphone setup; the operator keeps no dedicated SIP parameter page, and that walkthrough was published long ago. Confirm the address, port and mode with the account manager before you promise the venue a working number.

What to configure on the provider's side: sign a corporate contract for IP-LINK Digital → ask the account manager for the line's SIP parameters and the confirmation code → provide the “Static IP” from the "Server" tab and ask for it to be allowlisted → register the installation address for 119 calls → agree the list of permitted outgoing numbers and the G.711 codecs.

Pitfalls ⚠️

• The parameters are not officially published — everything here needs written confirmation.
• The standard contract requires the PBX not to be exposed directly to the internet. Raise our setup with the account manager in advance: ask for IP authentication with an allowlist and attach a description of your security measures.
• One credential means one registered device: with two registrations the last one wins, and parallel use requires a separate operator service. Our PBX holds one registration per trunk, so do not also register the same line in a softphone.
• The number of lines is capped by headcount — a small venue will not be given more than a couple of lines.
• Emergency calls 112/119 may be restricted by contract, and the address used for 119 comes from the contract rather than from the location card.

Sources: IP-LINK · business service overview · internet telephony service terms, rev. 01.12.2024 (PDF) — 10.09.2026.

More providers: parameters come from the account manager#

These companies do offer, or can offer, a trunk to your own PBX, but they do not publish the server address, port, authentication mode or codecs — everything arrives by email after an application. Fill in the form from the sheet they send, and take your questions from “What to ask the provider”.

• 컴네트워크 (ComNetwork) — the Korean 3CX partner, selling "GLOBAL SIP": a SIP account or trunk for the customer's IP PBX with cheap international calling. The company openly warns that an account alone is not enough — "the IP PBX settings, firewall, codecs, outbound policy and number conditions all have to line up" — and that number and outbound terms depend on the country and carrier. ⚠️ The product is aimed at outbound international calling, while a venue needs inbound Korean numbers: ask about this before paying, together with transport, codecs (G.711 over UDP) and whether our address must be allowlisted. The second risk is that the company's default scenario is "we will install 3CX for you" rather than "we will trunk into your PBX".
• 세종텔레콤 (Sejong Telecom) — an independent operator with its own backbone and a VoIP quality certificate from the Korean ICT association. It is interesting because independent operators are more willing to hand SIP lines to integrators, but it publishes no parameters and no description of a trunk for a third-party PBX. ⚠️ Enquire by email or phone through the corporate department: you need a 070 number plus a SIP credential or IP authentication towards an external PBX with a static address; confirm codecs, the number format in inbound calls and the concurrent call limit.

Operators with no trunk for your own PBX#

• KT — the largest fixed-line operator. Its range includes 기업인터넷전화 Centrex (the operator's cloud PBX) and biz (on-premise), but the headline benefit of biz is "switching equipment leased free of charge", meaning KT installs the IP PBX itself. Connecting a third-party PBX over SIP is absent from the product description; the only public mention of SIP interworking is in their contact-centre FAQ, and it refers to interworking with KT equipment, not to a trunk into a tenant's cloud PBX. The base tariff is ₩2,200 per line per month (₩1,100 when bundled with internet for 3–5 years). If you do discuss a connection, tell the account manager up front that the PBX is cloud-based with a static IP and ask whether a trunk without their on-site equipment is possible.
• SK Broadband — the "인터넷전화 실선" product: ₩3,300 per month, their own IP phones (Moimstone IP460S/IP390G/IP700B, HYC-P1200) and porting from another network. There is no separate description of a "SIP trunk into a third-party PBX" on the public page. Ask the corporate onboarding centre 1670-0099 directly whether a SIP credential can be issued for a third-party IP PBX without their handsets, and in which mode. ⚠️ The sales model is tied to their terminals with instalments and an early-termination penalty.
• LG U+ — 기업 인터넷전화 comes in three flavours: basic, centrex and 교환기구축형 (DCS) with the customer's own IP PBX on site. The practical blocker here is harder than at its peers: the operator will not disclose SIP data to subscribers as a matter of policy, and without a password there is nothing to enter into our PBX. The consumer myLG070 line historically registered against the lgdacom.net domain with the number minus the leading zero as the username, but the operator does not issue the password, so that route is a dead end. Only the corporate DCS track via 1544-0001 is worth discussing.

International providers with Korean numbers#

Cards for the popular international providers are already in the catalogue when you add a provider — the server address and mode fill in automatically. The Korean specifics:

• Telnyx — Korean numbers are available, but with full local KYC: a contact phone number, a copy of a passport or ID, a Korean company registration certificate, a local application form and proof of address no older than 3 months. Usage must be business only; private use is not allowed under their rules.
• Twilio — local (+822, Seoul), national, toll-free (+8280) and mobile numbers are offered; everything except mobile is sold to businesses only. It requires a 사업자등록증 (business registration certificate) and the Korean registration number, an address inside the number's area (a PO box is not accepted), and a signed corporate application form with the company seal or the CEO's signature. Twilio does not sell Korean local, national or toll-free numbers to resellers and ISVs. Twilio has no 070 numbers — Korean developers point this out specifically.
• DIDWW — only international (A-Z) trunking is available for Korea, with no local trunk: you get an outbound route, but no inbound Korean numbers.
• AVOXI, Global Call Forwarding, United World Telecom and similar — all of them have "South Korea SIP trunking" marketing pages with no parameters and no document requirements; in practice this is forwarding on top of the same local licensees. Check what you are actually buying before you pay.
• ⚠️ The overall conclusion. A foreign company without a Korean legal entity will realistically not get a local number — with both international marketplaces and local operators it comes down to a business registration certificate, corporate verification and an address in Korea.

Number porting#

• Number porting works in Korea for both 070 and landline numbers: the application is submitted to the new operator, which runs it through the number portability centre; the registration fee is paid by the subscriber.
• ⚠️ Not before six months. You may only change operators once six months have passed since activation or since the previous port. An application will also be refused if there is a month or more of unpaid debt.
• A landline number is tied to its area. A subscriber who has ported a landline number must stay within its numbering zone; moving outside it limits the porting service.
• ⚠️ Register the line to the company, not to a person. Corporate lines are capped by headcount, and the caller ID change service requires both numbers to belong to the same holder — a number registered to a private individual will cause trouble on both counts.
• The 119 address is part of the contract. When the installation site changes it must be updated with the operator, otherwise the call will reach the fire station serving the old address.

Rules and paperwork#

If it does not work#

1. The operator refuses to hand over SIP parameters. This is not a configuration error: KT, SK Broadband and LG U+ do not disclose trunk data to subscribers. Put the line with ClawOps or Wyz070, or negotiate a separate corporate interconnect.
2. Registration fails with ClawOps. Check the transport: their route only accepts udp and encrypted tls, while our PBX works over UDP and TCP without encryption. It must be UDP.
3. Inbound calls never arrive even though registration is green. With ClawOps inbound traffic does not follow the registration but a route to our PBX address: make sure the number has SIP routing enabled, the endpoint carries sip:<our IP>:5060, and that the address itself is taken from the “Static IP” field on the "Server" tab.
4. Outbound calls are rejected. Most likely “Show as” holds a number outside that operator's pool: ClawOps rejects such a call outright, and with carriers it is also a legal violation checked daily. Leave the field empty.
5. Calls to a representative 15XX/18XX number never reach the PBX. Such numbers cannot be routed to our PBX — they can only be forwarded to your own 070, with the trunk kept on the 070.
6. Two numbers, but calls all land on one line. A landline 02 number and a 070 number sharing their last seven digits are indistinguishable for routing — pick numbers that differ within those digits.
7. 112 and 119 cannot be dialled. Our PBX does not send numbers shorter than four digits, and internet telephony restricts emergency calls by contract anyway. Emergency calls are made from a mobile phone.
8. Silence one way or both ways. Check the codecs: neither ClawOps nor Wyz070 documents them publicly, and we need G.711 a-law or µ-law, or G.722.

Causes that are the same in every country are in “If calls do not go through”.

Frequently asked questions#

Can we connect our KT, SK Broadband or LG U+ number to the PBX?#

As a rule, no. All three sell internet telephony bundled with their own on-site equipment (a leased switch, centrex or their IP phones) and do not release trunk SIP parameters to subscribers — at LG U+ this is stated policy. That leaves two options: take a separate 070 number from a provider that offers trunking, or negotiate a bespoke corporate interconnect with the operator's account manager.

Which provider should we start with?#

If you need a number quickly and predictably — ClawOps: a 070 number is self-issued in minutes, the trunk documentation is public, and both the route to our PBX and the outbound credential are covered. If the venue wants an established operator with a contract — Wyz070 (삼성 와이즈070) and its IP-LINK Digital product, designed for a customer-owned IP PBX.

Do we need a Korean company?#

In practice, yes. Local operators ask for a business registration certificate and corporate verification, and cap the number of lines by headcount; international marketplaces want the same — Twilio additionally requires an address inside the number's area, and Telnyx a Korean company registration certificate. A number in a private individual's name, let alone a foreigner's without a Korean entity, is not going to happen.

Will emergency numbers 112 and 119 work?#

Do not count on it. Operators explicitly state that emergency calls may be restricted for internet telephony, and that the address forwarded to 119 comes from the contract (the terminal installation address), not from the location card. On top of that, our PBX does not dial numbers shorter than four digits. Keep an ordinary mobile phone in the venue and brief the staff.

Can we connect a representative 15XX or 18XX number?#

Not to the PBX: with ClawOps only forwarding is available for such numbers, and an attempt to point them at a SIP route is rejected. The working arrangement is to keep the trunk on a 070 number and forward the representative number to it.

How long does provisioning take?#

With ClawOps — hours: signup, corporate verification, enabling the trunk add-on and issuing a number are all self-service. With a carrier (Wyz070, the big three's corporate tracks) — weeks: paperwork, review and installation take from several days to several weeks.

Sources#

All links checked on 10.09.2026.

Providers

• ClawOps — creating a SIP endpoint: https://docs.claw-ops.com/api-reference/claw-ops-api/sip-trunks/create-sip-endpoint
• ClawOps — route to an external PBX: https://docs.claw-ops.com/api-reference/claw-ops-api/sip-trunks/create-sip-origination-route
• ClawOps — issuing a SIP credential: https://docs.claw-ops.com/api-reference/claw-ops-api/sip-trunks/create-sip-credential
• ClawOps — IP allowlist: https://docs.claw-ops.com/api-reference/claw-ops-api/sip-trunks/create-sip-ip-acl
• ClawOps — numbers and routing: https://docs.claw-ops.com/numbers
• ClawOps — pricing: https://claw-ops.com/pricing
• 삼성 와이즈070 — IP-LINK: https://www.samsung070.com/biz_ip_link_info.html
• 삼성 와이즈070 — IP-CENTREX: https://www.samsung070.com/biz_ip_centrex_info.html
• Samsung SDS — internet telephony service terms, rev. 01.12.2024 (PDF): https://image.samsungsds.com/kr/etc/contracts/__icsFiles/afieldfile/2024/11/21/wyz070-service-agreement_241201.pdf.pdf
• 컴네트워크 — SIP service: https://ippbx.comnetwork.net/sip/
• KT Enterprise — 기업인터넷전화 biz: https://enterprise.kt.com/pd/P_PD_CC_CI_002.do
• KT Enterprise — 기업인터넷전화 Centrex: https://enterprise.kt.com/pd/P_PD_CC_CI_001.do
• KT — internet telephony service terms, rev. 08.2026 (PDF): https://m.corp.kt.com/attach/board/BS00000005/56/%EC%9D%B8%ED%84%B0%EB%84%B7%EC%A0%84%ED%99%94%EC%9D%B4%EC%9A%A9%EC%95%BD%EA%B4%80.pdf
• SK Broadband B world — 인터넷전화 실선: https://biz.skbroadband.com/page.do?menu_id=P01010200
• LG U+ — 기업 인터넷전화: https://www.lguplus.com/biz/all/product-service/phone/voip-all/B000000149
• 세종텔레콤 — 세종VoIP: https://www.sejongtelecom.net/pages/service/line_internet

Regulator and law

• KT — terms on preventing outgoing number substitution (PDF): https://corp.kt.com/data/attach/196/%EB%B0%9C%EC%8B%A0%EB%B2%88%ED%98%B8_%EB%B3%80%EC%9E%91_%EB%B0%A9%EC%A7%80_%EC%9D%B4%EC%9A%A9%EC%95%BD%EA%B4%80.pdf
• Detailed guidelines on preventing harm from spoofed numbers, notice no. 2015-32 (PDF): https://mkt.tason.com/download/postman_detail_guide.pdf
• Korean Law Information Center — 전기통신사업법, article 84-2: https://www.law.go.kr/LSW//lsLinkCommonInfo.do?lsJoLnkSeq=1019731109&chrClsCd=010202&ancYnChk=
• KISA — countering outgoing number spoofing: https://www.kisa.or.kr/1020602
• Government24 — telecom operator registration: https://www.gov.kr/mw/AA020InfoCappView.do?HighCtgCD=A09006&CappBizCD=14400000011

International providers

• Telnyx — South Korea DID requirements: https://support.telnyx.com/en/articles/5467053-south-korea-did-requirements
• Telnyx — Korea, Republic of virtual phone numbers: https://telnyx.com/phone-numbers/south-korea
• Twilio — South Korea regulatory guidelines: https://www.twilio.com/en-us/guidelines/kr/regulatory
• DIDWW — SIP trunking services in South Korea: https://www.didww.com/voice/global-sip-trunking/South_Korea

Related pages#

• Connecting a provider's number to the PBX — the general steps, trunk modes, network and connection checks.
• Setting up SIP phones — how to connect desk phones and DECT handsets to extensions.