Cartrack device has not been working one only find out when repoting the ****** vehicle

I have been using cartrack for as long as I can remember,I only have to find out that their device that they installed in my vehicle was not working when I need their assistance when my vehicle was ******.No one give me a feedback when I call them they kept on telling me that they are still busy checking but they can't locate their device. It seem like I have been paying for something that does not work for years maybe, but I have to find out when my vehicle was ****** and I need their assistance. My question to them is that what is it that I have been paying for all these months because they kept of deducting money from my account every month. I also wanted to find out that how are we protected as customers from this kind of issues. I am also thinking that maybe this have not happened to myself only surely they are so many customers out there who are paying for the services that are not been offered. Is it possible to get my money back for the months that I have paid but the device was not working. I also want to cancel my contract with them with immediate effect