How many times must I cancel my contract?

I have been trying to cancel my contract since July 2020. The contract period has lapsed, i.e. had it for 2+ years now, and I have made 3 separate request via the retentions department to cancel my contract as well as an instance of an outreach from headoffice to do so.

5 Months later, I'm still being debited and despite the most recent feedback from the retentions department that my final debit date would have been Nov 14, I receive an SMS that I will be debited on 2020-12-31 for my contract fee. I'm bombarded with requests to upgrade my contract (which should have been cancelled in July) and members of the organisation who call me, claim to have no means to escalate the situation?! Ridiculous!

This process is broken, and needs immediate attention for the greater benefit of all your customers, but in my particular case, this is theft. Should I simply block the debits from my bank account, it will likely have this reflect poorly on my credit rating. I have the mind to lay a charge against Cell C with the relevant ombudsman for my money back as there is seeming no avenue I can make use of to actually bring my contract to close.