Bad account experience

I have done a change of ownership on my MTN Contract in October/November 2022. The first month MTN deducted the amount of the handset from my account, as well as the account of the new owner. I have asked for a credit of R740.00. Up to date, I have not received the credit note. Since December 2022, MTN disconnects my airtime. Every time I have to call Customer Care, which replies they can see there is an outstanding credit note, and that my line shouldn't be disconnected. They then reconnect my phone. Happy days.... but when the new month starts, I have to do the process all over again. Why cant MTN just update my account???