Yealink T42G, T46G & T48G BLF CallerID <-- unknown

Hello everyone,
I’ve already tried the yealink forums for a solution, but maybe the issue can be solved by asterisk itself.

I have the following setup running:

  • FreePBX with Asterisk 13.9.1.
  • Trunks and Extensions are using chan_PJSIP.

The problem starts with the BLF feature because the inbound caller ID is not being displayed correctly on the notificationof the phone. It shows

“[Extension being called] <-- Unknown”.

Is there anything I can configure, so that the phones will show the correct CID, which calls my BLF Extension ?