Cell C *****ing my money every month despite me cancelling in Jan 2020

I had CFibre from Cell C as my internet provider , I cancelled in January 2020 with my notice period being February 2020 as of March 2020 I have a new Provider. Cell C is continuously taking money off my account every month despite me contacting them and advising them of their error. I’ve had to reverse these payments every month , I have called them and emailed countless times , I have confirmed cancellation notification by resending my cancellation notification to them showing the date I informed them of the cancellation. What else must I do , it is for this bad service that I cancelled CFibre in the first place. The service is so bad and so is their Fibre, stay away from them

Felicity Adam CF121673