Canceled contract and double payment by Cartrack

I have been with Cartrack since 2015. The contract finished long time and was on month to month with them. It happens that I missed the monthly premium. They called to advise and requested the banking details on the 17th of July. 2023. I had to call them for the banking details which eventually received after I told them to cancel the contact. I paid their premium. I receiv the message that to ownethem R107. 29 which I paid. They still said I owe them the same R107. 29. May you please assist as now they are estorting money for nothing as the contract was canceled on the 17th. I don't want to deal with them. Please. Thank you.