ADT: poor service + blacklisted without my knowledge

Joined ADT last year after experiencing a break-in, but tried cancelling once another company became more active in my area and had more response vehicles available. Received a statement with a ludicrous cancellation fee of R 1222, and several phone calls trying to convince me to stay with ADT. Tried explaining that the response time after an alarm sounds is the most important motivator for wanting to move to another company, and told the operator that I am not prepared to pay for a service I am not happy with, and certainly no cancellation fee for a service I am not even receiving anymore. Never heard back from the operator again, and assumed that the matter is settled. Only to be phoned yesterday by someone from ADT telling me to settle the account (after which I could not hear her anymore on the other end of the line). Sent an email asking about it, and just received another phone call telling me that the amount has been written off as bad debt and that it will reflect on my credit score. Beware of signing 24 month contracts with ADT; ask how many response vehicles they have dedicated to your area. Would not use them ever again!