Bad service

I have a contract with netstar tracker for more than 2years now and it's now I regret getting into a contract with them, I have panic button in my car as an early warning signal last month it was not working and I reported it and they came and fixed it after a long time of calls and complaints finally after 2 weeks they fixed it and while I was communicating with them I find out that they have been billing someone on my account which I was not aware until I called them nd complained about the tag and the panic button that was not working, they said they fixed it and they will send me the report to see that it's indeed my account that's been billed even now am still waiting after 3 months and still waiting. Recently I was almost high jacked and I pressed the panic button more than 3 times after 30 minutes between and no respond to the point of me pressing it more often and no respond luckily I managed to get to the police station where they escorted me, we called the tracker to ask if they received any signal on my car and they said no their serve must have been off, the following day I pressed the panic button again nd still no respond until today no respond I press it every morning when I come to work but nothing clearly showing that am paying for something that's not working and they debit every month, I asked one of the caller if my car was ****** what will happen if their tracker is not working nd am paying he said he will be sorry, will sorry bring my car back no it won't... Am not impressed at all this is all wrong please assist me please