Paid up letter granted but, says i have overdue installments

My brother took out a cellphone with Blue label. he finished paying off the phone and was granted with paid up letter but every time when he wants to purchase something in credit, blue label appears. he has bee blacklisted. Please help him sort this out. the complainant is Kagisho Motlhale ID number ***. i have also tried to check his credit and i found that Overdue Amount is R5,339 but they granted paid up letter.