Cancellation of policy!!!

I had a car accident in November 2013 and requested cancellation of my tracker policy since the car was written off. I didn't want to use tracker anymore in my new car because after the installation, my pre-tensioner cables for Airbags were damaged and I had a fault alarm light that I fixed myself at my expense. This is unprofessional. I was informed it's not possible to cancel since I'm on a 36 month contract that i never agreed to. Now the 36 Month term has expired but I'm still being debited. Please cancel my policy with immediate effect. I do not want anything to do with tracker anymore.