Very poor service from ADT.

I cancelled the contract via email in January already and followed it up with another email to find out if they received the first email but I got no answer. They send me an account to pay but I'm paid up until end of February. I phoned them to tell them to take my AJAX alarm system of their system. But to no avail. Two nights in a row now my alarm screams and ADT phones me. I phoned ADT yesterday and the lady that helped me said the technical department will phone me back. I'm still waiting. I'm not going to pay if they send someone to my house to look. I'm already with another company and I can't afford them both and why will I want to have two security companies.