...if its not turning off dont try to turn it off, cuz if the button doesnt work it wont turn back ON. take it to the cell phone place, wherever that is, and see if they can help you or get you a new phone.
what you can do is you can press the 'End' button for about 5-10 seconds. it should shut off.
if not try opening your battery cover on the back of your phone and take out the battery. That automatically shuts off the phone. if you put the battery back in and hold the 'Call' button for 5-10 seconds, it turns back on.
If none of these tips help i'd go to your local carrier store and ask them for advice.
take ur battery out of the back and keep it out for a couple of minutes then put it back in...if that doesnt work go to the store u bought it from and there is something else wrong with it.