Account handed over

I cancelled my subscription with ADT security on the 02/11/2014 via email and had no response from the company. They continued debiting my account and I reversed the payments as the cancellation was valid. They only cancelled my subscription in March 2015 after numerous emails and calls to them asking why they still debitting my account. Now they have handed my account over to a collections company without calling to to settle the outstanding balance. When I did contact them they advised me that they no longer have mu file and that I should speak to the collections company and not them. Between March 2015 and November 2015 no one has ever contacted me from ADT to confirm why payments were not received from December 2014 till March 2015. However they did call me to ask why I has cancelled my subscription. I am fed up with ADT and I want my name cleared and the amount ritten off as I followed their processes and due to negligence from their side I'm getting punished. Enough is enought!!