Inability to cancel my contract

I cancelled my contract when it expired. I did not receive any further bills, but in November I noticed that the debit order is still running. Since then I have been phoning them on the case, I I have supp**** the cancellation form three times and they tell me they cannot attend to this problem. It takes over a month to resolve. When I ask to have it escalated to management then the call Centre assures me they escalate to the manager who will phone me. Needless to say this never happens. This is the first time ever that a simp,e issue such as a cancellation of service cannot be processed.