Contract cancelled but still being billed almost 3 months since the cancellation

So I cancelled my data contract in November 2022 after cancelling my voice contract in September 2022 but Vodacom is trying by all means to refuse to cancel it. Even after sending them a voice recording of my contract cancellation, they are still sending me invoices and statements which I do not know what for as the last payment for them was in December and do not owe them plus I destroyed both their sim cards so there is no way someone can use them. They refuse to cancel via email or any other way except for calling knowing very well that you wont have proof that you did cancel.