Our contract was to expire in July 2009. In June, due to the system kicking into an annoying beep in the middle of the night, and otherwise sitting useless in the "Error" code (apparently, that meant no communication from the system in our house to the monitoring service), we called ADT to cancel the service and step us through manual disconnection of the beeping system.
We were instructed, over the phone, how to disconnect the system altogether (what does that mean? NO MONITORING from now on!) and we were told the contract will be over in July, as originally signed for by a person who did not longer reside at the house prior to July 2009, and has been deceased for several months now.

Well, today is January 05, 2010. We have checked some bank accounts and discovered we are still being billed the monthly fee and that our contract has NOT ended in July 2009, as we were told!
We were told that, since we did not inform ADT in writing, the contract has not expired.
We told them that we feel it is unlawful to bill us for services that were not delivered (the system was disconnected) and we want out money back. We also requested to be provided with a name and phone number of the representative at the ADT head office in Calgary but, we were told, this information will not be given to us because "the head office will just send us back to our local office" (presumably in Edmonton, AB).
"Felicia" told us she will submit our request to the head office in Calgary, but they can only refund us for 3 months. She said she will know in a "couple of days" (we will follow up on this) of the status of the refund request.

We feel contacting BBB is in order and we are seriously considering filing the case with the The Provincial Court of Alberta, Civil Division. Since we were billed for, I believe, 6 months (for the non-deliverable service), suing ADT would be a matter of principle, we would not get rich on this nor we care about getting rich on this. We do, however, feel that someone should seriously do something about ADT's antics. Class Action, anyone?
Post here if you feel this might be a good way to get justice.