iphone 5 mic problem with lifeproof case on

Hello,

I have an audio problem when I'm in a conversation with someone else on my iPhone 5 (just upgraded it to iOS 8), which I recently received from a friend (for Verizon), and using it with T-mobile. The problem is that when the other person is talking they cannot hear me talk, which is frustrating as you can imagine. My friend gave me the phone with a Lifeproof case that he used. When I took the case off then the problem went away. My first thought was of some kind of audio feedback problem with the case design, however my friend used it previously for a year and didn't have this problem. My second thought was then maybe updating to iOS 8 changed the audio processing driver and now there is some problem with this case design. I guess I could get a different case but I would rather not. Any help is appreciated.