ADT refusing to cancel my contract

This company is ignoring my request to cancel a contract with them. I have sent them over 5 emails with regards, and, every time I call the contact centre or accounts department I am told someone will call me back or, put on hold for up to 10 minutes. This is causing a huge problem for me because they debit my account outside off the agreed upon amount and continue to charge me for "excessive responses" meaning my alarm has gone off 8 times (8 times!) during loadshedding which I cannot personally account for. I have tried to negotiate with them when the only person who responded to my request to cancel promised to refund me for all the erroneous charges. The timeframe given for these reasons was missed by them and they are not responding to my emails on this account rectification as well, neither are they ever calling me back every time I phone them and ask for resolution. I am now stuck as my bank cannot cancel the debits for me and are saying that ADT must be the ones to cancel my contract.