Singapore: SIP providers and connecting a number to the PBX

This page continues the general guide to connecting a provider's number to the PBX, which 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 the connectivity check. Here we cover what is specific to Singapore: why the familiar telcos will not work with your cloud PBX, who to buy a number from instead, and which numbers a foreign company is allowed to have at all.

The data was collected on 10 September 2026 from provider websites and regulator documents (IMDA, PDPC); links are in the "Sources" section.

In brief#

• A dedicated PBX is created for Singapore locations — Singapore is not on the list of countries where the server cannot be raised. The venue needs no permit of its own: the licence is held by the provider you buy the number from.
• ⚠️⚠️ The main divide in the country is telcos versus internet telephony providers. Singtel, StarHub, M1 and MyRepublic sell a SIP trunk to a PBX on the customer's premises and over their own network: Singtel requires a separate network interface and a static route into its network, M1 offers a "Static L3 VPN" variant, and MyRepublic's contract states plainly "between an on-premises phone system and our telephone network". Such a trunk cannot reach our cloud PBX. What works here are OTT providers and international operators.
• Where to start: Telxi — if you want the parameters up front and without any correspondence (it is the only one that publishes them: sip.telxi.com, 5060, UDP, registration); SIPTEL — if the venue is held by a Singapore company and needs a "landline" number from the 6 series: it has a plan built exactly for our setup, "we just forward call to the static IP of your PBX"; CalnCall — a local operator with online ordering, but on a 24-month contract.
• ⚠️ A foreigner will not be sold a 6-series number. Ordinary landline numbers 6XXX XXXX may only be issued to "domestic" subscribers in Singapore; a foreign company gets the 3XXX XXXX series — a fully functional number, but a VoIP one. The 6 series requires a Singapore resident or a company with an ACRA registration and a local address.
• ⚠️ Calling Singapore guests "over a cheap foreign route with a local caller ID" will not work. Since December 2022, at IMDA's direction operators block incoming international calls with spoofed +65 3, +65 6, +65 8 and +65 9 numbers. Outbound calls must go through a provider that actually holds a Singapore licence.
• ⚠️ Every number is eight digits, while the PBX matches a line by the last seven. The numbers 6234 5678 and 3234 5678 look identical to it — do not add two numbers that differ only in the first digit to the same account.

Numbers in the country#

• Country code — +65. There is no national (trunk) prefix such as "0": inside the country you dial exactly 8 digits, and in international format it is 65 plus the same 8 digits (+65 6234 5678).
• The first digit defines the category:

• In Lines enter the number exactly as the provider issued it: the PBX matches the last seven digits, so writing it with or without +65 makes no difference.
• ⚠️ The seven-digit trap. A Singapore number is 8 digits while only the last 7 are matched: the landline 6234 5678 and the VoIP number 3234 5678 produce the same tail and will collapse into a single line. If a venue has both a 6- and a 3-number, check this when adding the second line.
• Ask the provider in what form the number arrives on an incoming call. There is no single rule in the country: Telxi and international providers send the international format (65…), Singtel sends the national one (8 digits), and CalnCall's own guide puts the trunk user name in the number field — in which case the line cannot be told apart by number and the call goes to the general route.
• ⚠️ Emergency numbers are three digits, and outbound dialling that short does not pass through a trunk. Keep a mobile phone at hand for 999 or 995. Note also that for 3-series numbers a provider is not obliged to give access to emergency services at all — it only has to warn you about that.
• Codecs. Ask for G.711 a-law/u-law — that is what our PBX accepts. Some local providers put G.729 first, and we do not have it.

Who provides a number with a SIP trunk#

Telxi — the only one publishing its parameters#

An international provider listed by both 3CX and Yeastar among those certified for Singapore. The model is self-service: the trunk is created in the portal ("SIP trunks → Add new"), numbers are attached there too, and then the trunk is activated by support. It is the only provider in the country whose parameters are in a public knowledge base.

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

What to set up on the provider's side: create a SIP trunk and make its identifier equal to your main number — then the incoming call carries the number rather than an arbitrary login → attach the numbers on the "DID Number" tab in international format → ask support to activate the trunk → change the outbound caller ID if needed (the knowledge base has a dedicated article, "How To Change Your Outbound CallerID").

Pitfalls ⚠️

• Telxi does not publicly advertise Singapore numbers. The trunk parameters are known, but there is no "Singapore numbers" page; as of 10.09.2026, confirm the availability of +65 numbers in writing before paying.
• The trunk does not work until support activates it. A "green" registration line does not yet mean a working route — always make a test call.
• The codec list includes G.729 and Opus, which our PBX does not have. Make sure PCMA/PCMU (G.711) is enabled on the trunk side, otherwise the call will connect with no audio.

Sources: Telxi — connecting a SIP trunk to a PBX · Telxi — creating a trunk — 10.09.2026.

SIPTEL — a local operator that forwards calls to your IP#

A Singapore operator for small business holding an IMDA SBO (Individual) licence. What matters for us is not its cloud service but the per-channel plan: "suitable for establishments with their own inhouse PBX. In this case we just forward call to the static IP of your PBX" — which is exactly authorisation by IP. Terms as of 10.09.2026: SGD 25 per channel, minimum 2 channels, one Singapore number included, incoming calls free, no minimum term; activation takes about two days after the documents are checked.

Who gets which numbers (a licence condition, not the provider's whim):

Paperwork: a company needs an ACRA Bizfile extract and the signatory's identity document, an individual needs an identity document and proof of address, plus the provider's signed forms.

What to enter in the admin panel

What to set up on the provider's side: choose the per-channel plan → give the manager the "Static IP" from the "Server" tab as the call delivery address → state which numbers should be routed to this trunk → attach the documents and sign the forms. Ask right away: the host and port for outbound calls, the allowed codecs, in what form the number arrives on incoming calls, and from which address the provider sends audio. The full list is in "What to ask the provider".

Pitfalls ⚠️

• The provider does not publish technical parameters. Before signing, get written confirmation that the transport is UDP or TCP (not TLS only) and that G.711 is among the codecs.
• The 6 series is not available to foreigners. If the venue needs a "landline" number specifically, the contract has to be signed by a Singapore company.
• The plan counts channels, not minutes. Two purchased channels mean two simultaneous calls; the third caller gets a busy tone.

Sources: SIPTEL — pricing and Singapore numbers · SIPTEL — documentation requirements — 10.09.2026.

CalnCall — a Singapore operator with online ordering#

A Singapore company (part of the Cal4Care group) and the only local internet telephony provider on the 3CX certified list for Singapore; it claims compatibility with 3CX, Asterisk, Avaya, Cisco, FreePBX and Grandstream. Pricing as of 10.09.2026: SGD 69 per month for 10 channels, SGD 129 for 10 and SGD 199 for 30 channels; activation and a refundable deposit each equal one monthly fee, on a 24-month contract; a Singapore number costs USD 5 to activate plus USD 5 per month. Ordering and payment are online, followed by verification and a service agreement.

What to enter in the admin panel

What to set up on the provider's side: order the plan and the number online → pass verification → receive the email with the trunk parameters → route the purchased number to the trunk in the control panel → agree on G.711 codecs. Ask separately about the incoming number format: the provider's own guide puts the trunk user name, not the number, into the inbound route — if that still holds, matching a line by number will not work.

Pitfalls ⚠️

• A 24-month contract — this is not a "try it for a season" option.
• Parameters are not published on the site. The only guide with a server address that can be found is an archived 2016 copy, and it cannot be relied on: take the values from the provisioning email.
• The numbers are non-transferable. The terms state plainly that numbers bought from them cannot be moved to another operator even after the contract ends (except numbers that were ported in).

Sources: CalnCall — pricing and getting started · CalnCall — number pricing — 10.09.2026.

Telcos: a trunk only to an on-premises PBX#

The four national operators do sell SIP trunks, but to a telephone system physically located on the customer's premises and over their own network. For our cloud PBX this is a dead end, and it has to be established before signing, not after. There is no "what to enter" table here: if an operator does agree to accept signalling from an external address, fill in the form from the sheet you receive and take your questions from "What to ask the provider".

• Singtel — the country's largest operator. The official configuration template requires a separate network interface towards Singtel and a static route: "LAN will only cater for traffic to and from the SingTel servers", and the server address comes with the contract. Useful details: the product has neither TLS nor SRTP (which does not bother us), codecs are G.729/G.711, DTMF is RFC 2833, additional numbers are entered in national format, and a third-party caller ID is not supported — you may only present your own numbers.
• StarHub — "SmartSIP" — a trunk for IP-PBXs and corporate platforms: up to 1000 channels per trunk, per-second billing, 6-series numbers. ⚠️ Not a single technical document is publicly available: the mode, server address and codecs only become known from the contract.
• M1 — two variants: "Dynamic SIP Trunk" over their own fibre and "Static L3 VPN SIP Trunk" for a PBX with a static address. ⚠️ An L3 VPN is a dedicated link to the customer's site, not SIP over the internet; ask them directly whether they allow a connection from a third-party cloud address.
• MyRepublic — from 5 to 30 channels and hundreds of numbers, with porting of existing numbers. ⚠️ The contract states that the service is delivered "between an on-premises phone system and our telephone network" and only to "premises with an internet connection in Singapore", and that the customer must be ACRA-registered with a Singapore UEN.
• ViewQwest — an internet provider with telephony: the retail voice service is available only together with their fibre, while the business trunk is sold under contract. ⚠️ There is no public documentation; the key question is whether they will deliver a trunk without their link and to an external address.
• Hoiio and Toku — Singapore platforms that list a SIP trunk among their services but publish no parameters: Hoiio's trunk page was unavailable on 10.09.2026, and Toku's help centre is closed to automated reading. Confirm the status of the service with their sales department.

International providers with Singapore numbers#

Cards for the popular international providers are already in the catalogue when adding a provider — the server address and mode are filled in for you. What is specific to Singapore:

• Twilio — spells out the local requirements in more detail than anyone: a 3-series number (+65 3…) is issued to a legal entity with an address in any country, while a 6-series number requires a company registered in Singapore with a Singapore address; toll-free numbers go to legal entities only, and individuals are not sold local numbers.
• DIDWW — certified by Yeastar for Singapore specifically, sells +65 3 numbers through its panel and API, and supports both credential-based and IP-address authorisation.
• Tata Communications — a wholesale operator from the 3CX certified list for Singapore, selling under contract.
• Telnyx, DIDLogic, Zadarma, Sonetel and other aggregators offer +65 numbers delivered over SIP; the paperwork requirements are the same: the 3 series for foreigners, the 6 series with local documents.
• ⚠️ One general caveat. A foreign aggregator saves you the local paperwork but not the local rules: outbound calls to Singapore subscribers are better terminated through a provider with a local licence — an international route with a spoofed +65 gets blocked on the network.

Number porting#

• Portability is mandatory for mobile numbers and ordinary fixed-line service, and also for IP telephony services on 6-series numbers — to the same standards as basic telephony. The application is filed by the receiving operator; timelines and document sets differ between operators and are not published publicly.
• ⚠️ Nobody is obliged to port 3-series numbers. That is the main risk of a "VoIP number": once it is printed on your signage and menu, the venue is tied to that provider. CalnCall states this in its terms outright — their numbers are non-transferable even after the contract ends.
• A toll-free 1800 number can also be moved between operators, but it is worth having only if the venue really takes calls from all over the country.
• Register the number to the company, not to an employee. A number held by a contractor or a manager leaves with them; besides, a "number in an individual's name" in Singapore is only possible for a resident.

Rules and paperwork#

If it does not work#

1. The operator says the trunk is up, but "Check connection" fails. Most likely you were given an interconnect inside the operator's network: Singtel, M1 and MyRepublic deliver the trunk over their own link to the customer's site, not over the internet. Such a trunk cannot reach a cloud PBX — you need a provider that works over the public internet.
2. Registration is green but calls do not come. A Telxi trunk only starts working after support activates it: a successful registration is not the same as a working route. Write to support and make a test call.
3. The call connects but there is silence in one or both directions. Check the codecs: some Singapore providers put G.729 first, and our PBX does not have it. You need G.711 (a-law or u-law) or G.722.
4. Incoming calls arrive, but on the wrong line. Check that the provider sends the number rather than the trunk user name (as CalnCall's guide does), and that the last seven digits of two numbers have not collided — see the trap in the "Numbers in the country" section.
5. Outbound calls are rejected. Almost always it is the caller ID: in Singapore a third-party number is stripped on the operator's side. Leave "Present as" empty.
6. The provider only offers TLS. Our PBX will not accept an encrypted trunk — ask for plain UDP or TCP: most providers have it.
7. Short numbers cannot be dialled. The three-digit emergency numbers 999, 995 and 993 do not pass through a trunk — that is a limitation of outbound dialling, so use an ordinary phone for such calls.

Causes that do not depend on the country are in "If calls do not go through".

Frequently asked questions#

Which provider should I start with?#

If the venue is held by a Singapore company and needs a "landline" number — with SIPTEL: it has a plan built exactly for our setup (calls are forwarded to the PBX static IP), a minimum of 2 channels and activation in about two days. If you want the parameters up front and without correspondence — Telxi: the server address, port and mode are published. CalnCall is for when you want to order everything online and are not put off by a 24-month contract.

Why can I not simply take a trunk from Singtel or StarHub?#

Because the big four sell a trunk to a system physically located on the customer's premises and deliver it over their own network: Singtel's configuration template explicitly requires a separate network interface and a static route into its network, M1's static-address variant is called "L3 VPN", and MyRepublic's contract says "on-premises phone system" and "premises… in Singapore". Our PBX lives in the cloud and has no such link.

Do I need a Singapore company?#

For a 6-series number, yes: it is issued to a Singapore resident or a company with an ACRA registration and a local address. A foreign company can buy a 3-series number (+65 3…) — it works the same way but is not obliged to support porting or access to emergency services. International providers such as Twilio sell the 3 series to a legal entity with an address in any country.

Can I call guests showing a Singapore number?#

Only through a provider with a local licence. Since December 2022 operators block incoming international calls carrying a spoofed +65 3/6/8/9 number — an attempt to save money on a foreign route will simply end with the call never arriving. And you may only present numbers from your own contract: a third-party number will be replaced or the call rejected.

What if the venue has two numbers — a 6… and a 3…?#

Check the last seven digits. The PBX matches a line by exactly those, so 6234 5678 and 3234 5678 are indistinguishable to it and will collapse into one line. If the tails match, ask the provider for a number with a different ending or keep the numbers in separate accounts.

Is a recording notice mandatory?#

Yes. There is no separate "telephony" recording law in Singapore, but the general personal data protection act applies: notify the other party before recording starts and obtain consent. Enable the spoken notice in the location settings. Remember the Do Not Call registry separately: marketing campaigns, including calls to business numbers, are prohibited without explicit written consent.

Sources#

All links checked on 10.09.2026.

Regulator and numbering

• IMDA — National Numbering Plan, Issue 2, February 2026 (PDF): https://www.imda.gov.sg/-/media/imda/files/regulation-licensing-and-consultations/frameworks-and-policies/numbering/national-numbering-plan-and-allocation-process/imda-national-numbering-plan.pdf
• IMDA — Licensing and Regulatory Framework for IP Telephony Services (PDF): https://www.imda.gov.sg/-/media/imda/files/regulation-licensing-and-consultations/licensing/licenses/iptellg.pdf
• IMDA — Annex B: operators' anti-scam measures, January 2024 (PDF): https://www.imda.gov.sg/-/media/imda/files/news-and-events/media-room/media-releases/2024/01/opt-to-block-incoming-international-calls/annex-b.pdf
• IMDA — Services-Based Operations (SBO) Licence: https://www.imda.gov.sg/regulations-and-licensing-listing/services-based-operations--sbo--licence
• PDPC — Do Not Call Registry and Your Business: https://www.pdpc.gov.sg/overview-of-pdpa/do-not-call-registry/business-owner/do-not-call-registry-and-your-business

Providers

• Telxi — connecting a SIP trunk to a PBX: https://support.telxi.com/support/solutions/articles/43000707929-how-to-connect-your-sip-trunk-to-3cx-or-other-pbx
• Telxi — creating a trunk: https://support.telxi.com/support/solutions/articles/43000707769-create-sip-trunk
• SIPTEL — pricing and Singapore numbers: https://www.siptel.io/singapore-virtual-number.php
• SIPTEL — documentation requirements: https://www.siptel.io/requirements.php
• CalnCall — pricing and getting started: https://www.calncall.com/get-started
• CalnCall — number pricing: https://www.calncall.com/pricing/did-numbers
• Singtel — SIP Trunking Singapore: https://www.singtel.com/business/products-services/communication-collaboration/sip-trunking/sip-trunking-singapore
• StarHub — SmartSIP: https://www.starhub.com/business/products-and-services/enabling-my-physical-office/office-phone-solutions/office-line/smartsip.html
• M1 — Business SIP Trunking: https://www.m1.com.sg/business/products/telephony/sip-trunk
• MyRepublic — SIP Trunking: https://myrepublic.net/sg/business/sip-trunking/
• MyRepublic — Business Voice Service Specific Terms and Conditions (PDF): https://myrepublic.net/sg/wp-content/uploads/2022/02/Business-Voice-Service-Specific-Terms-Conditions-v20.04-Updated.pdf
• ViewQwest — OneVoice FAQ: https://viewqwest.com/sg/residential/faq/onevoice/

International numbers and compatibility

• Twilio — Singapore regulatory guidelines: https://www.twilio.com/en-us/guidelines/sg/regulatory
• DIDWW — SIP Trunking Singapore: https://www.didww.com/voice/global-sip-trunking/Singapore
• 3CX — certified SIP trunk providers for Singapore: https://www.3cx.com/partners/sip-trunks/singapore/
• Yeastar — certified SIP trunk providers for Singapore: https://www.yeastar.com/itsp-partners/singapore/
• 3CX — configuring the Singtel SIP trunk: https://www.3cx.com/docs/sip-trunk/singtel-asia/

Related pages#

• Connecting a provider's number to the PBX — the general steps, trunk modes, network, connectivity check.
• SIP phone setup — how to connect desk phones and DECT handsets to extensions.