MTN SHIULD BE VOTED OUT OF SA!

I was due for an ugrade in Jan this year but because my mom could not keep her original number and was given a new number with uncapped data and airtime we decided to return the device aswell as the sim and cancel the contract2 days later, however till now money is being deducted for the returned device when we went in to the MTN store we were told the device was never booked in as a return nor was the contract cancelled on the system, we cannot find our cancellation form anywhere what steps can be taken against these ridiculous fools?