unit not working and struggling for over 1 year to get Tracker to sort it out, still under guarantee

It has been a year that I have phoned Tracker to change my device which is not working (it still under guarantee, as it was only 1 year old when this starterd). Tracker actually informed me that it is not working properly per sms. i have phone more than a dozen times to get this sorted. Each time they promise that the technicians will contact me or that they will call me back in 2 days time, but that never happens. This started Sept 2018, so it has been 12 months with absolutely no service from Tracker, but I pay my premium every month...for what? Last time I phoned was on 03/07/2019 and was PROMISED again that the technical team will contact me in 2 or 3 days time. It is nearly 2 months later and still nothing Plan number ***