Tracker Billing issues and zero response!

Simply useless and unresponsive!! Have 2 cars with tracker for past 4 years. Decided to continue even though had met with continuous challenges with billing. no one to speak to etc Had a new unit installed 3 weeks ago, Wat a disaster. Install was fine however billing , charges etc have been a nightmare since then. Have been sent the incorrect invoice and charges 4 times now. Have asked someone senior to call, obviously there is no one senior as no one has called me yet! If this is how the billing goes can you imagine how it will be if someone *****s my car I regret having extended my contract with them, wen my other come sup at year end I will try someone else, there are many ......