Service was not requested

I’ve had an account with MTN for more than 15 yrs, in December 2019 my payment increased and I didn’t query it however, when the increase escalated in March 2020, I called the Call Centre and they promised to escalate the issue to their billing unit. This was not done instead the installments increased drastically. Upon further inquiry I was informed that we have been billed out of bundle services. I don’t understand how this happened because all these years I had my spending limit fixed at 0.00. I’ve been paying my normal monthly installments at a branch store but my service has been disconnected. I was informed that I now owe R24000.00. I want MTN to fix this urgently as it has negatively impacted my credit ratings. After this mishap, I will be moving to another service provider.