Voice barely audible during incoming call

[jolouis]

(12-04-2018 06:17 PM)Chris708 Wrote:  This is a cloud server of which I do not have control. I can call their service and have them do something but the odd thing is that this doesn't appear to happen with any other phone at their site.

Agreed if you have physically swapped out the phone it's probably not an issue with the phone itself. Since you don't have access to the server to do investigation/troubleshooting, a few things to try that I can think of:
1) Program a new extension number and change the account on the phone to use that. If there is something wonky on the server it could be related to the config/handling of that extension, so hopefully creating a new one from scratch might work around it
2) Firmware up to date?
3) Try a different phone model if you have one (T42 or T48) just to be 100% safe if possible.
4) Try a different network drop/port on the switch?

Also, have you done a syslog level 6 on the phone and been able to reproduce the issue? If so you can open a ticket with Yealink support and see if there is anything they find in the log file...