Monthly deduction without a service rendered

I would like to share my experience with ADT Security company, my alarm went dead 4 months ago, I informed them, about it, I have tried to contact them several times to try to resolve the matter but I they have been sending me from pillar to post, i i even twrote them a cancelation letter but they never cancel my alarm , they have been deducting money in my account for 4 months now, they are declining money but I don't have an alarm and they know it, I don't receive and services from them yet they keep on deducting my money, I'm not happy about the treatment they are giving me, I'm under a lot of stress about this.