Beame device not functioning

I have a beame tracking device fitted in my car by matrix. Since the device was fitted, everytime I called to test the device they say that my car cant be tracked or they have no comms with the device. Despite everything, Matrix wants their money every single month for a device that is not even working. This month they deducted their own debit order by changing the date of the debit order without my consent. I did order the company to cancel the device and stop taking debit orders because the device in my car is faulty so the operator once told me to drive around with my car to see if its working. My point of view is that they should be able to track my car no matter if its standing still or moving. How does a company expect you to pay something if it has no use?