I just googled to see if there were known issues with the Plantronics Voyager Edge's microphone because I'm having that same exact issue!
I just bought mine only 4 days ago, and thought maybe it was not properly adjusted in my ear so that the extended microphone wasn't touching my face-some Bluetooth headsets, I think, the mic portion must be touching your face, I think for picking up vibrations better to hear your voice-not sure though.
Anyway, most, not all of my calls, people can barely hear me or they say I'm breaking up, and I never had mic issues at all with my Bose headset!
I'm going to contact Plantronics directly and report this issue to them and also what others have said about this same exact issue with their units.