Netstar not cancelling contract after multiple communication

I have sent multiple emails to Netstart asking them to cancel my vehicle tracking debit, with no response. The first email was on 10 November 2023. I have sold the car and moved from South Africa on 25th November, but Netstar continues to debit my account every month and does not respond to my constant emails requesting for the cancellation. I am now living in Ireland and cannot afford to call them on the phone.