my hell with MTN

A settled account balloons to R32000 i bought a laptop through MTN in 2013 while i was student. Once i started working, i subsequently settled the outstanding amount. Th contract amount was about R4000. In 2015 i had paid off everything. after 6 months, i started getting huge amounts debited from my account by MTN. when i queried these, no one knew what they were were for. after lodging this complaint, the amounts stopped a bit. themn i started getting call from a law firm that i now owed R32000 . I have been unsuccesful in getting help from MTN. i have been in contact with both their legal department and an executive from the customer care division. after I provide them with all the information, including sworn affidavits, they stop responding to my emails. this has now affected my my credit rating and i cant even get into huge purchases.