Charged by ADT AGAIN following cancelation 4 month

My ADT account was taken over by the new tenant in August 2015. I received written confirmation from ADT confirming this. Yet every month without fail I receive an invoice for R2378.25 and every month I call the call centre. And every month I am told my account balance is R0.00. In October 2015 I submitted a Hello Peter complaint and was assisted by customer services. I was told there was a system error which was now corrected, and my credit rating had been updated accordingly. BUT guess what I just got an invoice for the 4 month since my cancellation! This is completely unacceptable, what do I have to do to update an ADT account I should no longer even have! ADT you are negatively impacting on my credit rating EVERY month. At this rate I won't be able to rent another property at which to use your services even if I wanted to! The sad thing is that your previous response turned my complaint to a compliment. You have just undone all the good work and no amount of good service will improve my perception of ADT. In fact you are lucky that all I discuss is my billing issue and not the service I received from you during my contract. If I receive another invoice I will discuss that next!