ABSA personal loans ****mers

My loan with ABSA is up to date and I did not miss a payment but one month I paid through eft due to the debit not going through but with ABSA they informed credit bureau that this account was never paid for that month and has been handed over which was not true. This account was never handed over and I have paid it accordingly. The worst thing is when I lodged a complaint with them they refused to correct with Transunion. You cannot say the payment is missed while you have received the full installment still on time.