Bad service and exploitation

I have a car tracker since 2022 i have been paying with debit order . To my suprise since last month they are harassing me with smsz and calls that i owe them R189 i made calls amd they could not tell me what it is for instead they mized me . Now the amount is changing to R39 still no communication i also sent them cancellation request there is no communicatiom what so ever i am just call every . Bad service just exploitation . What annoys me the most is few months ago i called them about the information on their app not being accurate and they did not care to assist now they sending sms everyday . This contract was just a waste of time . I would rate a zeto if there was a chance