Account debited even contract has expired

I signed up for mix Telematics on 14 July 2018 which was for 36 months ending 15 July 2021. I received a call towards August 2021 offering me a month to month subscription since the initial contract was coming to an end, which I declined because it was double the previous amount. I removed the device in August 2021 and replaced it with the new company I had subscribed to. To my surprise in August 2021 I got billed, I sent an email to *** on 18 August 2021,to immediately cancel the month to month contract as I had not accepted it and my contract ended in July. Since August till December they continued debiting, and never responded to my emails. From January 2022 I disputed/stopped the debit orders and than started receiving calls that my account had been handed over to lawyers and that I owe R 220.77. Even after explaining to the lawyers and sending numerous emails to MiX Telematics, I have gotten no response but they continue to send the invoice monthly. I am very disappointed in how they conduct their business, even after my contract has ended they are still trying to rip me off.