I spent about 60 minutes on the phone with them today and they didn't back down (they'll take it off if I use a dumb phone, but they'll still charge me for this month).
Chargeback. Your credit card company takes a dim view of people who try to bill you for things you haven't ordered.
Be careful about that. If you chargeback and the large company fights back, you could be in a world of pain with the phone company AND the credit card company!
Just hang up and dial back. Do this a few times and you'll find an agent who can help. I imagine this auto plan thing is to avoid massive per minute charges they would normally charge
Have you red your original contract? Is this something covered in it?