The Phone app wont record audio?

I can make and receive calls but the other party cannot hear me even when on speaker phone. Other applications seem to record my voice just fine; I can call people on Skype and I can record my voice on the camera app, Snapchat, etc. The phone app is the only app that seems to have trouble with this; the other party literally cannot hear a single noise from me; does anyone have any idea what is happening?