Falsified documents

I got a month-to-month sim only data contract in March 2015. In July I queried something about the billing and I realised that the store had registered this as a 24-month contract. I went into the Garden Route Mall store and asked them to explain. They had many excuses and in the end admitted they had made a mistake and everything will be cancelled, without any penalty or cancellation fees. It is now one year later and they are still taking money from my account. They handed me over to Telkom's debt collectors, NUDEBT, because according to the billing department I should not reverse the debit order every month. This can not be legal, how are they allowed to do this to me? I did not sign a 24-month contract. I have all my proof and correspondence from the last year that I have been complaining and trying to clear my name due to Telkom's mistake. Why has the George branch not been investigated for this? WHEN WILL IT STOP! It has been one year of humiliation and anguish for me. I hate Telkom!