I have a client with 2 new 7960G phones and new CS50 headsets with the lifters. The client states that he can hear dial tone but the microphone is not working on either unit/phone. He has tried the new CS50's on other Cisco phones and of course it works just fine. I am looking for a path to take to troubleshoot this issue. I spoke with Plantronics whose response was basically not our problem. If someone could point me in the right direction on this I would appreciate it.