my iphone 4s turned off while playing music and wont turn back on. i try to plug it in to charge but it just makes the sound it always does when you plug it in but it still wont turn on. i tried to plug it into my computer but it says it cannot connect to my iphone because it has a lock on it but the screen wont power on for me to unlock it. i tried to hold the power and home button to reset but it did not work. any help?