Complaint

I have a contract with MTN and I have been paying a monthly contract of R198, where I receive R100 airtime. Then to my surprise in the month of April this year R5000+ was debited from my bank account and then immediately I went to the bank and reversed it as there was no agreement between MTN and I that this should happen. I've have been going back and forth calling them to sort this out. Amidst trying to sort this out I was told that my package has been changed to an unlimited package which I have never agreed to . I am very upset as this ruins my credit record all because of the negligence done by MTN and to top it off I've been trying to sort this out clear my name for months without a positive outcome.