MTN is debiting my account unauthorised

My name is Ntandoyenkosi Sandile Mkhungo. I have been with MTN since I started using a phone many years ago and I am absolutely disgusted by MTN Pinetown service. I have 2 contracts with MTN, about 3 months ago I walked into the Pinetown MTN store when one of these was about to close and spoke to a lady named Fathima who then sold me an upgrade of a blackberry Z 10 for the going price of R210 per month for 24 months according to the contract Documents I have Signed and we have agreed Upon. They charged me excess and all the necessary opening charges in july which I was aware of and had been advised would be a once of payment and then thereafter it would be R210 going forward as advertised. Well month 2 came and they charged me R488 so I called in and complained and they apologised and told me they will reverse extra charge to next month's payment and I Still Have The proof of those message's sent by the lady Fathima advised by her manager. Today instead of reversing the extra funds they took without authorization or agreement they have Taken another R610 charging me excess twice according to my statement. I demand that money reversed back into my bank account and no where else.