MTN do not honour cancellation requests.

I see that MTN does not respond or acknowledge complains on here but I'll add my little story to the void. In August 2023 I attempted to cancel a 5G month-to-month contract at the Fourways Mall store by physically handing the router back to the consultant and signing the necessary cancellation document. Fast forward to now and I am still receiving invoices and have just had a negative credit score impact due to supposedly being in arrears even though it is a month to month contract and I paid up to and including the notice period of cancellation. Multiple emails with supporting documentation and phone calls to customer "service" are futile. At a loss as to what to do.