Mtn cancellation issues

Good day...MTN is pathetic! I've been struggling to cancel my contract since June, I recieved a SMS in June giving the date that my contract will be cancelled, they debited me the end of June and I thought it's all done, now its September and they still debited me... after numerous SMS's saying that it will be cancelled... what the hell are they still doing in my account... I am tired and disgusted at MTN's **** service, I am now going to my bank to block them from debuting my account and MTN can do as they please... can you please assist?