********* behavior by MTN

I had an account with MTN and I settled the account in December 2019, I was provided with a settlement letter. I found out in June 2020 that MTN has listed me for non payment on the basis of an account that I have settled six (6) back. This is ********* behavior and the audacity for MTN to do this without even contacting me is very strange. This companies are preying on people livelihood as this is significantly affecting my credit score.