Supersonic keeps billing cancelled FLTE and already returned router packages

I can confirm this is not yet resolved. I cancelled my fixed LTE start of november for cancellation 30 November 2022 (Since it is billed in advanced i have given 30days notice and was called, confirmed it will be cancelled at end of November, the router was also collected and has been returned to supersonic) The waybill of RAM courriers for returned router and simcard, Waybill SUPE07-***3 and Reference S*** has already been received by a Supersonic returns employee named Zodwa Manyanga , but my account still states R498 outstanding for a bill of R499 billed for service 01/12/2022 - 31/12/2022 , I have cancelled it for end of november so there was no bill to be issued for the invoiced ammount for December as it is cancelled and router has been returned, I was only advised of a final bill with just the courrier collection charge, KINDLY URGENTLY arrange for this bill to be urgently cancelled and my final bill to be correctly issued of just the router fee, that should be the last bill ever, Thank you