Wrong Billing

I went for a phone upgrade on the 17th June 2015 at Krugersdorp President Hyper complex. It is a top up, upgrade which will be R149.00 every month. Instead of that money to be debited wrong amount are debited. July 20th R395.80 was debited and on 20th August R401.49 was debited. I logged a complain on the 4th of Septmeber 2015 till today my matter is not resolved because even the shop assistant whom i have been communicating with is unable to assist me. To me this is a bridge of contract because did not agree and sign up for this monthly increment. This amount keeps on increasing because 20th October i am still going to be billed an extra amount. If this matter is not attended to urgently will be forced to take further steps. So kindly assist because honestly is not nice for your money to be taken without your permission. Ref no: ***