Cell C is a ****

I was on contract with Cell C for 2 years and the contract ended in 2019, because I didn’t call the cancellation department to cancel the cell phone contract, Cell C decided to still continue with the debit orders which I refused to pay for. Fast forward 2022 beginning of the year, I find out I’m blacklisted, I was supposed to pay almost 12000 rands, which i paid so they can clear my name and called them from their Cell C offices at ilanga mall to cancel the contract, which I was told the next day was cancelled. I asked for proof that my account has been cleared and till this day I did not receive proof that my account has been settled. Two months back till today I have been receiving emails with final letter of demand from them that I’m owing money again. This Cell C is really a ****, I have been calling and emailing and nothing is being done. The cell phone in question doesn’t even work anymore nor the SIM card, i don’t know what to do at this point, clearly they didn’t send the clearance letter so they can continue ******** more money from me.