Debit after contract cancellation

I had a 36 months contract with MTN, which expired in May 2025. I made it clear with them that I'm not upgrading on several occassions and even called to cancel which the cancellation was confirmed but to my surprise I was still debited this month with extra R218 on top of the usual amount that they used to debit. And suddenly when I call, I fail verification of the same information I provided when I requested cancellation because they don't want to explain why they debited, with an extra amount on top. I WILL NEVER EVER RECOMMEND MTN TO ANYONE BECAUSE THEY DON'T WANT TO CANCEL CONTRACTS WHEN YOU WANT TO CANCEL.