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