Frustration with ADT Security

Few months back i installed an ADT alarm system. I then experienced so many problems from the technician who installed the alarm system to their response time. On the 15 December people tried to brake into my house and i pressed the panic button and scared them off but the response car came 50 minutes later and this is not for the first time. I cant activate the alarm at night for it gives false alarm. i have been calling reporting this so many times but two months later i haven't been helped. i just want to cancel this useless ADT contract.