Hate Telkom service

I canceled my wifi contract with telkom in August 2021, I was informed I will pay until end September 2021 then the contract will be canceled. I received emails and sms' to this effect to. Then I got billed for October 2021 again, after enquiry I found that I'm now on a prepaid contract without signing such a contract. I've asked again for them to cancel the prepaid contract and it was said I'm on prepaid and that's it. What should I do???