2005 Chevy Uplander, has OnStar headhunt on roof by map lights...since yesterday while driving it constantly turns on and off by itself. You can press the cancel button and it ends the call, but 5 seconds later it will call again but cancel before it ever even has a change to ring. Is there any way to disable the system? (without ripping head unit out of roof). I would be nice to have it fixed just in case we needed it in an emergency situation but don't want to go to dealer.