A SIP 403 FORBIDDEN error during outbound calls typically indicates that the SIP provider is rejecting the call due to authorization or permission issues. Here are the common causes and steps to troubleshoot: • Authentication Issues: Verify that your SIP trunk credentials (auth_username/auth_password) are correct and not expired. • Insufficient Permissions: Ensure the authenticated account has permission to make outbound calls to the destination number. • Number Restrictions: Check if the calling number is authorized for outbound calling. • Destination Blocking: Confirm with your SIP provider if calls to the specific destination number or region are blocked. • Account Limitations: Verify that your SIP provider account is active, has sufficient balance, and is not suspended. To resolve this issue: 1. Check your outbound trunk's authentication credentials. 2. Verify with your SIP provider that your account is in good standing and the calling number is provisioned. 3. Test calling different numbers to see if the issue is destination-specific. 4. Review your SIP provider's call logs for detailed error information. 5. Ensure the number format matches your provider's requirements. If you need help troubleshooting a specific aspect of your SIP trunk configuration or investigating particular call patterns, let me know. Sources: livekit/livekit_agent_dispatch.twirp.go | livekit-api/livekit/api/twirp_client.py | pkg/sip/outbound.go | Agents telephony integration | LiveKit Docs