Mtn is debiting my account incorrectly

I was sold a phone and contract over the phone. Only to find once I received my purchase, that I was completely mislead. So as per the T & C 's, I returned the purchase within the stipulated 7 days. That was several months ago. I called the relevant call centres, went the relevant mtn direct stores. Apparently it's all done, but Mtn is still debiting my account. When I don't even have a mtn contract or prepaid mobile.