ADT continue to send me an account no matter what

I cancelled my ADT contract in December (for the second time) because of their ********** accounting administration. I originally switched to SSG and was happy, but I was dragged back into the ADT fold when they bought SSG. I received an account from ADT on February 17th, and rep**** immediately via email. I also tried to phone, but was unable to speak to anyone - no answer. Still, email sent, no reply, so problem solved, I thought,. Received another account today. Tried to phone again. Listened to canned voice telling me how wonderful they are for 8 minutes until my call was disconnected. I cannot phone them, they ignore my emails... but keep on billing me for a service I didn't get. The first time I cancelled (years ago) I had the same problem until I resorted to hellopeter. I was assured then that my debit order had been cancelled, only for it to go through a few days later. This is why I cannot deal with ADT accounts. They don't respond to email, I can't get through on the phone... yet the bills come month after month.