Terrible service and unauthorised transactions off my account

Four years after closing my WiFi account and giving one months notice to do this in 2020 when I went to work abroad, my account was suddenly debited for more than R2000 in 2024 by Supersonic out of the blue. I have tried to get hold of the company and that is a nightmare in itself as they hardly ever answer the phone or respond on their WhatsApp line, or to emails! I have spent a fortune on international calls trying to get this sorted out, to no avail. Their customer care is appalling ! When I finally reached someone this week I was told it was a cancellation fee from a cancellation made in 2022, however , I told them I was not even in the country in 2022 and this was not from me. I was told someone would call me back and they never did. This is *****ulent. I cannot get anyone to acknowledge my messages or respond and block my bank details.