Mtn contract cancelled, but debiting my account

I was offered a contract by Mtn, I thought it over and then cancelled the contract, I do not have the handset and it was never delivered. Mtn has been debiting my bank account since January 2016. I have made numerous calls, had to go to the bank for the last 2 months and have the debit order reversed. I have been to Mall of the South where I was told, I have to sort it out myself. I have been to The Glen, where I had to have a copy of my ID certified as well as a sworn Affidavit done at the Police Station, I was given a reference number by Mtn, on contacting them 5/5/2016 I was told that the reference number does not exist. It has cost me bank charges to have a stop order put on my account, the debit order amounts changes every month, hence the reason why my stop order hasnt been stopped, as per the bank if the reference number or the amount changes Mtn can still debit my account every month. I have spent over R100.00 in airtime trying to get hold of Mtn, to no avail. Can anyone assist me please.