Blacklisted me for defultin R9 payment that I don't know of

Since 2022 I have been trying to get assistance from MTN but in vain. MTN added and submitted an incorrect default to the credit beareu about me owing R9. This has caused tremendous finincial and reputational harm for me. Having my name blacklisted for a R9 that I have no idea where it came from and when I call MTN no one can explain what the R9 that got me blacklisted was for. I have been calling mtn and visiting stores but I did not get assistance, I kept being sent from pillar to post.