poor service

I must say mtn are pathetic. I had a 2 years contract with them, I finish paying last year October. I went to the glen where I purchased the phone to inform them I don't want to renew my contract, and I was advised there was ***** somewhere I need to go to police station for avidavit which I did, to my surprise every month they debit 3200 in my account, I called several times spoke to different consultant to fix this, but still it's not fixed. I've never skipped a payment or whatsoever. Now I will be listed as a slow payer which I'm not. Please help me, this has been going on and on for 4 months.