Unfair credit rating with Cell c

Good day, I app**** for a new contract in the week, and the consultant that assist me advised my contract was declined and that my credit score did not allow my application and the person mentioned that I had a contract in 2002 that was not paid up and that was also the reason for the decline of my application. The account was settled and paid in full, my question is why 19 years later this is still not cleared on Cell C site, my credit report does not show the i have debt with cell C.