Was surfing on the phone last night while it was plugged in and the phone froze for a minute or so then just turned off. It was fairly hot so I unplugged it from the power. Tried turning it on by the button as it did this the other day a couple times but came back on every time. Its been a few days now. But I've tried plugging it into AC and my laptop via USB and neither bring on the charging light. From memory it had about 20%+ battery so it isn't flat. I've tried holding, repeatedly pressing the buttons. What do I do?