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Wixzel Voice does not sell phone numbers or minutes. You connect a SIP trunk from a carrier you choose, and your carrier bills you directly at your rates. That is a deliberate trade. It means one more step before your first call, and it means we are never between you and your telephony provider — no markup, no resale margin, and no reason for us to care which carrier you pick.

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What you need

Any SIP provider will do. From them you need:
  • a host — sip.carrier.example
  • credentials — username and password, if they use registration
  • your numbers, and whether inbound calls are delivered to that trunk

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Connecting it

transport is udp, tcp or tls.
The password is encrypted at rest and is never returned by the API again — including to you. Store it wherever you keep the rest of your carrier credentials.

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Registering a number

A number must belong to a trunk before it can place a call:
Give it an inbound_agent_id and calls to that number are answered automatically by that agent.

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Carrier-side setup

Your carrier needs to know where to send traffic. Point the trunk at the IP of your Wixzel Voice deployment on the SIP port, and allowlist that IP if your carrier requires it.
An open SIP port is scanned for toll fraud within hours of appearing. Only endpoints matching a trunk you have configured are accepted — there is no anonymous endpoint — but keep your carrier’s own fraud controls on regardless.

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When a call fails

400 number_not_on_trunk means the number has no sip_trunk_id. Calls are placed over your trunk, so a number that is not on one has nowhere to go. If calls connect but there is no audio, the usual cause is RTP not reaching the server — check that your firewall allows the media port range, not just the signalling port.