Cancellation / Complaint

I have tried to get this matter sorted . My mom had a stroke in September 2020, We sent Vodacom a letter on the 19th January 2021 cancelling her telephone number and explaining the situation to them . We received a email back saying that customer care had received our letter. Up until today they are still billing my mother and putting the debit order through her bank account. We have been into Vodacom to sort this out, but they still keep charging her , her phone has been off since last year , nobody is using it but vodacom seem to find a different amount every month to charge her with Please can I get some kind of assistance to this matter.