MTN Laptop contract

I have a contract with MTN, i gave them my payslip and my bank statement told the sales person i get paid on the 25th, to my surprise first month last year they didnt debit on the 25th, they debited on the 1st of the following month, i went personally to ask why, the guy who helped me said he will fix it. following month same story, i went again, and this time they didnt get any money on the 1st. it bounced. then they told me they have fixed it and they will debit on the 25th, but even today they are still debiting on the 1st and it always bounces. i went there to enquire they tell me they have handed me over to their lawyers i ask how because i never got any call from mtn saying i dont pay? i was not away the money was not going through. why wait for a customer to come and enquire first. i am sick and tired of MTN and want to cancel their contract, bcs i see their mission is to make people blacklisted. Never in my life i have not paid my creditor, NEVER, my name has never been at the credit bureau, i have never been called by any lawyer asking for paymen they say i must pay R5900 plus R1660 if i want to cancel??? what is this? i must take this matter to NCR complaints department.