yi-hsuan Lee
Hi Team,
Thank you for the guide. I have reviewed the documentation, but the issue persists. As requested, here are the specific details regarding the outbound call failures:
Call IDs:
  • 019cd28e-ee73-7dc0-8774-4b33fce4c815
  • 019cd271-dbe2-7580-b7e7-1e0cc8f879d5
  • 019cd241-38ca-7140-abfc-db2dd09afb6d
Error Details:
  • Error: call.in-progress.error-providerfault-outbound-sip-403-forbidden
  • Direction: Outbound only
  • Behavior: Every outbound call results in a SIP 403 Forbidden error. This is generated by Vapi's SBC before any SIP INVITE reaches Twilio; there is zero SIP traffic in the Twilio logs, notifications, or Monitor events.
Vapi Resources:
  • Credential: 713f5ca1-f791-43bb-8a8b-030d3c75909b
  • BYO Phone: 1f47d073-a346-406e-96d0-b27974c8aaa1
  • Twilio Trunk: TKe6276e2bb66438f3f3c2d82e554397d4
Configurations Tested (All failed with the same 403 error):
  • IP ACL authentication only (Vapi SBC IPs: 44.229.228.186, 44.238.177.138)
  • Credential List authentication only (digest auth)
  • Combined IP ACL and Credential List
  • Wide-open IP ACL (0.0.0.0/1 + 128.0.0.0/1)
  • No authentication
  • Direct IP gateway instead of trunk URI
  • Exact format from Vapi documentation (no auth plan)
  • New credentials and phone numbers
Recent Changes:
None. This setup has not worked since the initial configuration.
Please let me know if you need any further information to resolve this.
Best regards,
Evan