Bad service

I canceled my 2 data contracts in november 2021, the last debit order went off on the 1st December 2021. Now in February 2022 I got a missed payment on my credit score. I went in to MTN Ilanga nelspruit to get to the bottom of this. I had to pay R804 to settle the account. Definitely not recommending MTN at all. How do I need to pay for a service that was canceled in November and I paid the 1st December?