Why do a I have a missed payment after payment the whole amount

Unhappy with the service regarding settling my phone contract. I settled and closed my contract in July after paying off the balance but my ClearScore credit just came saying that I have a missed July payment for Vodacom. How did vodacom not update that the account has been settled or the balance has been paid in full after I called 3 months before to notify that in July I will be settling the balance on the contract. I followed every process required by vodacom to ensure that I settle and cancel the contract. I was promised that the contract has been successfully cancelled, I have the receipts and massages from vodacom that state that the account is settled and cancelled but I have a missed payment on my name now. I did all this in person at vodacom Acornhoek Mall so vodacom please fix the issue before experian gets involved.