Paying for a damaged tracker unit

I fitted a tracker unit from Altech Netstar in Feb 2014 and have never skipped a payment ever since. Last week, out of curiosity I wanted to test if my unit is still working ,I pressed a panic button more than once and no one called and non of my secondary numbers were called. The following day I called Altech to find out what happened and I was told they never got a signal. The lady I spoke to promised me that she will run a test signal and will send me a report the following day via email and will also call, non of this ever happened. I called the centre again on Tuesday 17/10/2017 and spoke to a gentleman called Fani (Fanyana) and he told me that he will do the same test the lady was suppose to do and also email me the results and call the following day, non happened. Before he ended the call he told me that my unit is old and I need to upgrade, I agreed to upgrade and he transferred me to upgrade where they advised me of the new units and their functions, I agreed on upgrade and was advised that they will call me the same day or the following day to upgrade. I am still waiting for their call even today. When I call the centre to follow up, agents are hanging up calls on me. Now I am paying for a service that is not even working, all this time I thought my car was safe and armed only to find out now after all these years of paying that they are not picking up a signal from my unit. What would have happened if my car was ****** or hijacked and only to find out that it cannot be traced?