BAD SERVICE FROM MTN

I have been an MTN user for the past 16 years and it is with sadness to mention that I am now been listed as a bad payer, MTN never missed a payment from me for the past 16years. because MTN failed to investigate my complaint and rather decided to have me listed. I had a contract renewal with MTN, and my account was debited with R3500 instead of R700, When I noticed this, I immediately contacted MTN, and I was told my data limit was increased and OTP was used to increase it. I did not understand because I did not create any OTP and I have a customer pin with MTN which only I know. I ask for the numbers that are creating OTP to be blocked, and I was told it will not happen again, to my surprise the following month an amount of R3200 was debited and when I called, they said someone is using data, which does not make sense, I get data from them, and I buy my own airtime and they should be able to see that. I was told to make an affidavit at the police station confirming that I did not use data and airtime, which I did and sent to them, then a few weeks later my account was blocked. I got frustrated and reversed both debit orders and stopped paying MTN because I did not feel it is right to pay for a service I did not use.

I need your help to resolve this, losing the MTN contact number has cost me a lot, I lost most of my clients because I had to use a different number with Telkom. Cell ***