Lack of Service Delivery

We recently found out our tracking device is faulty. This was picked up by my husband as he contacted Tracker after not receiving any correspondence from them for over a year. The device was supposed to be tested by Tracker regularly, which they obviously weren't doing as they never notified him that the device was faulty. After much wait, a technician confirmed on the 18th of Nov. that the device is faulty and will need to be replaced. My husband was then informed that someone from the retention department will contact him, as he wanted to cancel the service. On the 23rd of Nov. someone contacted him to inform him that Tracker is willing to replace the device at no cost if he will sign a three year contract with them, for a fixed monthly rate (no annual increase). He was willing to settle for this, but after 4 more days (it is now the 27th) of not hearing anything from Tracker about replacing the device, he is seriously questioning Trackers ability to deliver on any promise. Our insurance insists we have this device. Who will be held liable if our vehicle gets ****** whilst the device is faulty? We have been and are still paying the monthly fee for no service whatsoever.