Reference number issue

A friend of mine had a 2 year contract with them which ended in 2024. But found himself with the record of having been in arrears for that contract. Upon contacting blue label connect, they promised to rectify it. They told him all was sorted and he requested a paid up letter,only to be given one with a reference/account number different from the one appearing on his profile. He has been trying to get this sorted for weeks now. How is that even possible?