Sounds on iPhone not working

Out of the blue, none of the sounds on my iPhone are working. The apps are soundless, incoming and outgoing messages don't make sounds, I can't hear it ring, no sound whatsoever. I have the ringer turned all the way up. I've tried charging and restarting my phone. This is my third problem on a week, do I have a dud? Or is this there a simple solution? Help!