iPhone 5 unable to hear or be heard during phone calls

My iPhone 5 can recieve and make calls but once the phone call connects I can't hear the caller and thet can't hear me. It happens on both incoming and outgoing calls. On incoming calls I hear the phone ring, answer it as usual, it connects and the call's time counter begins, I speak but hear no one. On outhoing calls I dial the number, I hear no ring tone but the call connects, then I can't hear the person I called and evidently from speaking to several people who have been on the other end they could not hear me. I've tested it out thoroughly, it's not connected to a Bluetooth device, the microphone works fine, the speakers work fine, the volume is turned up, it simply acts as though the phone has taken the call on both sides but there is silence on both sides. It makes no difference if I attempt to use the speaker phone. Please help me if you can, I have read through a half dozen threads on similar issues but only one thread described the same problem with no solution given.