Alright so my iPhone 4(AT&T GoPhone, iOS 6.1.2) is having a problem with voice calls. When I make a voice call and hit send, the speaker icon button lights up immediately and I cannot hear any audio. If I turn speakerphone off, I still can't hear the audio. All other sounds and functions on the phone work flawlessly, as well as calling from any of the various free calling apps that I have. The phone is not stuck in headset mode, and connecting a Bluetooth headset also does not work. An interesting thing to note, however, is that when a Bluetooth headset is connected I can only select speaker and the headset on the input selection menu. When I tried to press iPhone, it does not select. I have restored twice, once from a backup, then a full factory restore, no backup. Neither helped. Does anyone have any thoughts as to what might be causing this? Thanks.