503 Service Unavailable for specific phone number on SIP trunk

Telephony
1

This question originally came up in our Slack community and the thread has been consolidated here for long-term reference.

I set up a SIP trunk with multiple phone numbers. Some numbers work correctly, but one specific number returns “503 Service Unavailable” immediately from LiveKit.

All numbers use the same trunk, dispatch rule, and FreeSWITCH configuration. The failing number is configured in multiple formats (+1XXXXXXXXXX, 1XXXXXXXXXX, XXXXXXXXXX) in the numbers array.

2

The error Multiple SIP Trunks matched occurs when you define the same phone number multiple times.

If you add the same number in different formats (like +<PHONE_NUMBER> and <PHONE_NUMBER>) in the same SIP trunk’s numbers array, it can cause conflicts.

Solution: Only use one format for each phone number in the trunk configuration. LiveKit handles number normalization internally.