Harassment for monthly installment after canceling my contract as well as paying cancelation fee.

I have canceled my contract with Cartrack in October 2023 and the consultant in the accounts department told me that I am in credit with an amount of R1100. So my cancellation fee will then be the difference of R1300 which I have arranged to be deducted November 2023. This was done successfully, however cartrack than proceeded to debit my bank account for a second time for the monthly installment of R229. I reversed that due to my cancellation fee has been paid I am no longer contracted to them. Now I am being harassed by cartrack for this R229 installment. I have asked them how can they expect me to continue paying a canceled contract? They phone, message and email me for instalment not paid after they received the cancelation fee from me. The only response I get is that I must pay the installment to bring my account up to date. They must bring their records up to date!!! I also want to know why was I never called to be informed that I was in credit with R1100.00 for God knows how many months yet they continued to debit my bank account and kept it silent, had I not canceled my contract I would never have known of this credit on my account. YOU HAVE RECEIVED THE CANCELATION FEE OWED TO YOU AS ARRNAGED WITH YOUR ACCOUNTS DEPARTMENT. STOP PHONING ME, EMAILING ME, WHATSAPPING ME, FOR MONTHLY IINSTALMENTS!!!!!! I OWE YOU NOTHING!!!!!!