Impossible to close account of a deceased person

My ex-Wife passed away on 3 July 2021. I closed the account in store on 28 July 2021, and transferred the contracts to my account. The latter was done, however, despite settling the outstanding amount, Cell C never closed the account. In Jan 2022 I received a call about the outstanding amount (due to fees for failed debit order, AFTER 28 July 2021). I again submitted the documentation to the Cresta branch, the call center and the debt collections team. To my surprise the account has now being handed over to debt collectors. The right hand and left hand of Cell C does not know what it is doing.