Rachelle if you can't get your phone to Respond by trying what Commonsense suggested try pulling the Sim for 5 Min. then re-insert the Sim Card and try powering it Up if the Battery is Dead Charge it for at least 3 to 4 Hours after trying this and you can't get no response i would take it to the one of the Local Corporate stores and have them get you a new Unit..
It worked, my phone froze and would not go the unlock screen. I held down the power button and the decrease volume button and it turned the phone on. Crazy. Thank you for the suggestion.