MTN reported me to Experian for no reason what so ever.

I have been a contract subscriber with mtn for many years. I have a debit order set up for MTN. Couple of days ago I got a notification from my bank that MTN logged a account not paid at the end of July with Experian credit bureau. I check my score and I work hard to better my score because I want to buy property. I checked my bank statements. ALL mtn payments was made. What now? My score dropped by 23 points because I did nothing wrong. I want it fixed NOW.