I had the problem that my iPhone headset was not working properly anymore. The music playback went fine, but when answering a call the caller could not hear me. Also I noticed then, that I could not use the headset’s button to control call answering or iPod playback.
First of all I thought it was corrupted, because even on plugging it out and in again did not change anything in that misbehavior. To be sure it is not my fault, before claiming the Apple support, I restarted my iPhone.
Still not working and I even made a complete reset and restore. The solution is somewhat strange!
In microphone jack was some dust – just such a little that I could not even detect it on blowing into the socket or plugging the headset connector in with a smart pressure. With a wooden toothpic I managed to get it out. It was just a very little tiny fluff.
After cleaning everything went fine, again. So keep it clean and easy going!