How reliable is the tracking unit in your vehicle?

I have been a loyal Netstar client since Dec 2012 and installed devices in three different vehicles. Payments are done through debit order and the yearly increases have been paid timeously. When I tried to test the alerts on all my vehicles, none of them are active. I reported the problem to their monitoring department and was promised a response from the technical dept. Up to date, there hasn't been a response from technical. Upon enquiring with Netstar, I was told that the tracking units are obsolete and dysfunctional. So I have been paying for a system that did not meet the purpose it was intended for.

Netstar has offered an upgrade for a further 36 months which I refused. I have subsequently cancelled my contracts with Netstar and moved to another supplier.