My iPhone was working perfectly untill a couple minutes ago. I was talking on the phone for about an hour. When I ended the call I had 11% battery left, then I picked the phone up again 15 minutes later, and it's dead (turned off by itself). It won't turn on at all now, I even left it on the charger for 15 minutes... still unresponsive? Is my iPhone broken? It did get pretty hot during the call.