Bring your own phone number: Twilio, Telnyx or SIP

8 September 2026 · 5 min read · by the NordTell team

Your phone number is on the van, the website, the sign above the door and in a thousand contact lists. Nobody wants to change it to try a voice agent. You do not have to. The number stays where it is, at your carrier, and the agent answers it. Here is how that works for Twilio, Telnyx and everything else, and what to check before you switch it on.

The number stays yours

Bringing your own number does not move it. It stays in your carrier account, with your contract and your bill. What changes is where an incoming call is sent: instead of ringing a desk phone or a voicemail, it is routed to the agent. Take the agent away and the number goes back to doing what it did before.

This is also why the carrier's charges stay separate. The monthly rental and the per-minute price for the phone leg are billed by Twilio, Telnyx or your SIP provider as they always were. The agent's minutes are a different meter. Think of it as the line and the receptionist: you already pay for the line; the agent is the person who picks up.

Twilio and Telnyx: connect the account

These two are the easy path, because the connection can be set up for you. For Twilio you need the Account SID and the Auth Token from your Twilio console. For Telnyx you need an API key. You paste them into the carrier connection, and the link between your account and the agent's phone system is created automatically. Then you pick the number to import and choose the agent that should answer it.

If you have never used either, both let you buy a number in most European countries in a few minutes. The one thing to know is that some countries ask for proof of a local address before a number can be used. The carrier walks you through that. It is their process, not ours.

Any SIP provider or PBX

If your numbers live with another provider, or behind an office phone system, the generic SIP route works with any of them. You enter your provider's SIP server, a trunk username and a password, which is stored encrypted. Then, in your provider's or PBX's own settings, you route incoming calls for the number to the agent's SIP address, which is shown on the screen.

That last step is the one people miss. The connection exists, but until the provider is told to send calls to it, nothing rings. If inbound calls do not arrive, this is the first place to look.

What to check before you switch

A short list, in the order things usually go wrong:

1. The number is a voice number, not SMS-only, and it is active at the carrier.
2. Nothing else is answering it: an old forwarding rule, a voicemail service, a hunt group.
3. The right agent is assigned, and its language and opening hours match the callers.
4. The greeting says it is an AI, and the agent can transfer to a real person.
5. Call it from a mobile, then from a landline, then from abroad if you have customers there.
6. The blacklist works: block a test number and confirm the call shows as "Blocked".

Do this on a quiet afternoon, not on Monday at nine. Our test plan has the longer version.

One number per job

Give each agent its own number, and each client their own if you are an agency. It keeps the routing simple: a call arrives, one agent answers, one set of instructions applies. It also keeps the outcomes clean. You can see at a glance which line is busy and which is not.

Outbound campaigns deserve a number of their own too. People call back the number that called them. If that number leads to the same agent that placed the call, the conversation continues. If it leads to a general reception, it starts over.

You do not need to route everything at once. A common first step is to send only the after-hours calls or the overflow to the agent and keep the main line on the desk. Most carriers make that a quick change in their forwarding rules, and a quick change back.

Where NordTell fits

NordTell connects the carrier account you already own. Twilio and Telnyx are set up automatically from your credentials; any other SIP provider or PBX connects by pointing the number at the agent's SIP address. Imported numbers can be assigned to any agent in your account, removing one only detaches it, and a blacklist is enforced per workspace.

Numbers in the product · Overflow and after hours · Ask us about your carrier