Contract expired but debit order still goes through

I regret the day I took a 24 months Smart Broadband 20GB Wireless TopUp contract with Telkom in June 2020. The contract has expired after 24 months in June 2022 but guess what they are still deducting even after they called in May 2022 to ask if am I renewing the contract and I instructed them to cancel it cause I no longer need it and there is also very poor connectivity with Telkom in my area so I was just a waste to have it in the past 2years. the lady who had called me assured me that the contract will not be renewed. They are still deducting even now, I try to reverse the debit order and even stop it but they keep deducting. and I keep on incurring the bank charges for reversal. this is not on. I wrote them an email with no luck. I am a very disappointed and frustrated customer.