Last night my phone was casually working when all of a sudden, the screen froze on the active application. This happened before but usually it unfreezed or restarted, but now, the phone just turned off (screen went entirely black) and doesn't respond to anything (tried to hold power button, in combination with either & both volume buttons) for about 1 minute per combination. The phone doesn't respond to my charger being plugged in all night either...
Is there anything else I can try before having to take it back to the store?