SIP
403 Forbidden
The server understood the request but is refusing to fulfill it. Authorization will not help. The request should not be repeated.
When You See This Code
When the server policy denies the request regardless of credentials. Common for blocked numbers, restricted routes, or ACL violations.
How to Fix
Check server ACLs and routing policies. Verify the caller is permitted to make this type of call. Contact the server administrator if the block is unexpected.