If you're hearing on echo on your end and you’ve already tried adjusting the mic volume on the base it may be something called “configurable sidetone”. Sidetone lets users hear their voices played back in the headset and provides assurance that the phone is working.
This is an admin feature that was added to the Unified CM application. It is available for the following phones: 7971G-GE, 7970G, 7961G-GE, 7961G, 7941G-GE, and 7941G phones
How to fix the issue:
You will need to contact your phone admin for this step! (Unless of course you are the phone admin)
Set the Handset/Headset monitor variable in Cisco Call Manager for this phone to 'Disabled'. (This can be found in the configuration Window)
Time for a new headset?
Many Cisco phone Customers have switched to the Leitner LH270!