MTN SA legal and retention department poor service.

I had a wifi contract with mtn after a year or so I asked them to cancel this contract and I paid cancelation fee in time their agent made a mistake and send my account to legal for collection of R3000/+ and I have been calling mtn legal but their service is poor I have been blacklisted mtn and I am running a business but I can't get credit and I don't owe mtn anything I have sent several email to *** but no one acknowledge my emails you only received outomated massage 7days back I did send email called them on *** no one has ever called be back and what brother me is that from last year till today my effort and complain has never been acknowledged by MTN SA and their relevant department BA***