Ok so today in class i was adding a classmates number to my phone but ended up not finishing putting it in and just locked my phone on the add contact screen. A few minutes later when i went to go finish putting it in it would not unlock when i hit the lock button. The screen would just stay black. The only thing that made me think it just didnt all of a sudden break is that a green light in the left hand corner is blinking, like when you get a new message, so i know that it is still on. When i got home i plugged it into my charger but it did nothing. Help!