10 percent cancellation fee!!!!

Not insurance related but we had ADT security alarm system here at the S&B. I called them 5 days before my monthly automatic payment and told them to cancel my security programming effective the day I called. They informed me that it took 30 days to cancel and that I would still owe the next months payment. Well they didn't do the Auto Deduct but 6 days later I received a paper will for the next 30 days of service, which I promptly threw in the trash. I called and canceled the service before the due date of the next payment, and will be dammed if i'll pay for the next months service because they say I have to.