Cancelled contract

I called Vodacom 1 August 2023 to cancel my contract, insurance included. 8 September 2023 I received a statement billing me for the month even though my contract end date was 29 August 2023. I called them on 11 September to get clarity on why I'm being sent a statement even though I have made it clear that I am not going to continue with the contract. They assured me that it would be sorted, and I won't be billed. Then a debit order went off yesterday, the same amount that I disputed when I called during the month. Can they get this sorted out and refund me as I made it clear that I would not be continuing with the contract. I find it very disrespectful that we have to go through so much just to have our contracts cancelled, and on time.