Bad customer service

My contract with MTN was handed over to MBD Inc as I was not paying the account. In 2019 I had made an arrangement with MBD to pay ~R350 per month until I settle the account. I settled the account in November 2019 and till today the account still shows it's active and hasn't been removed from the credit bureau. I have made several calls to MBD inc and MTN to clear the account, they have made empty promises. A whole year has past and I am just fed up with them. MTN could easily send my account to the attorneys but they don't make any attempt to follow up and clear the accounts.