MTN Service down the drain

I have been a client of MTN for almost ten years now. I have three different contracts with them. never have I had any problems, but since last year December it has been one nightmare after the other. I upgraded my son's (9) tablet and data line which he uses for school. I specifically asked that the lines be capped at 5GB. In March money was deducted out of my bank account to the value of R 5400-00 and also my monthly subscription fee! on my bank statement it reflected that MTN has taken the extra amount off. I went back to the store where I upgraded my contract to find out what the story was, after I was advised by client service to do so. they informed me that WE changed the limit and we used our credit available. this came as a shock as this was NEVER explained to. I did not even know this existed and can be done! the money was not authorised to be taken. I have been battling ever since then with them to get the mess sorted out. no one seems to be able to help me. I will not be held responsible for this as I specifically requested the line to be capped. no one even told me that the limit could be changed as this is a top up account. should this not be part of the discussion when a package is upgraded! the shop in the K90 shopping centre in Benoni refuses to assist and keeps telling me it is my responsibility to pay. the regional manager also cannot assist me. the owner does not get back to me and head office refuses to assist me. they have now taken an amount again out of my bank account but it was returned due to insufficient funds. so now because of this, the monthly subscription fee was also not taken of. I wanted to pay my account but the MTN shop corporate cellular in the K90 shopping centre does not process payments? according to the Consumers protection act all that MTN has been doing is ******* and against the CPA. CAN SOMEBODY PLEASE GET BACK TO ME URGENTLY. I WILL NOT BE HELD RESPONSIBLE FOR AN ACCOUNT WHICH I HAVE NOT RECEIVED AND ALSO FOR SOMETHING THAT HAS NOT BEEN EXPLAINED TO ME. THE SERVICE IS SHOCKING. LEAST TO SAY ONCE MY CONTRACTS ARE UP I WILL BE WALKING OVER TO MTN'S BIGGEST COMPETITION AND I ADVISE OTHER CLIENTS TO DO THE SAME. GET THIS MATTER SORTED MTN SHAME ON YOU FOR DOING THIS!!!!!!!!!!!!!!!!!!!!!!