A customer is using Plantronics M22 headset amplifiers on their 706 phones plugged into the headset jack. On incoming calls, from station to station or outside when they press the headset button to answer the call, the headset button lights up and the phone answers the call. They can hear the caller, but the caller cannot hear them. This is an intermittent problem which has been happening for a long time. The 7100 is at version A5.02.00.E and the 706 phones are version 2.4.1 . They do not have a problem on outgoing calls. Has anyone else had this problem? If so, have you found a resolution? Only thing I have found so far is the Headset Compatibility Matrix.