Some user may find they can only hear one side of a telephone call when listening to calls. This is due to your speaker settings being set to Mono. They need to be configured to Stereo for the call to be heard in it's entirety.
Please click on the below link to set the speakers to Stereo.
http://yourbusiness.azcentral.com/change-headset-audio-mono-stereo-using-windows-vista-21664.html