"I've recently discovered God, and decided to disconnect from the Internet, as it is the tool of Satan. Tell me, have you accepted Jesus Christ as your savior?"
Alternatively, call, say you want to cancel, and if they give you shit just claim firmly you are unhappy with the service representative and hang up. With any luck they were recorded / reviewed. Just move on to the next guy.
Of course, usually these numbers are paid, so you pay a small fortune just to get to call someone that will do his job.
"I'm moving to (insert name of city owned by competitor)"