My nokia n8 froze help me please?

i have a nokia n8 and while i was watching a video on line it just froze out of no where now i cant turn it off or get out of anything. When i tried calling myself using mum's phone it went to message bank as if its turned off i put my sim card in my old phone and that still works fine so its definatly the phone thats not working it has an internal battery so i cant take it out to try and reset it. Any one had this problem? What do you recommend? And yes i checked it doesn't seem to have a reset button please help me