Dial ''#0''#, a test menu should appear. Click on loopback. You should see 2 or 3 microphones. Click on number 1 and speak into the lower microphone, you should hear it come out of your ear speaker. Do the same with 2 which is on the top. if one doesn’t work then the audio chip should be ok and the microphone needs replaced. If there is no sound from either microphone then your board has a fault.