Symptom
This issue mainly occurs on gateways products including TA, TB, TE, TG series. And the call source of the route is Register Type SIP trunk or Account Type SIP trunk. The Peer Type (Service Provider) would not have this kind of issue.
Cause
It's a hidden drawback of the dialplan.
Solution
Use Non-Simple mode for the IP to Port route. And fill a dot in the DID Number field.
