Inbound Calls - Can't Hear Caller Issue

[Leo_B]

Hiya,

For the last several days, one of our customers reports 'increasing' number of inbound calls issues - the office staff can hear the callers, but callers fail to hear them. Quite often a bunch of extra calls from customer resolves the problem, and a significant number of calls from outside doesn't seem to experience 'can't hear caller' at all. All office extensions have option 'PBX delivers audio' enabled, Firewall Check detected no issues, Unifi-powered firewall hasn't been changed for months, yet we're still looking for solution. Any ideas or hints?

Appreciate your response in advance!

3CX Version: 3CX Enterprise 8 SC 18.0 Update 7 (Built 312)
Server OS: Debian 10 4.19.282-1
Is the 3CX Server Hosted: no (Vultr-powered VM)
IP Phone Make/Model/Firmware: Fanvil X210 v2.4.12, X6U v2.4.12
Provisioning Method: SBC
Trunk Provider: Vitelity
Has the Firewall Checker passed: YES
Are custom Phone Templates being used: NO

 

[JohnS_3CX]

Hi Leo,

The firewall checker only tests the first and last few audio ports.

Can you please confirm that you are forwarding the entire range from 9000 to 10999?