Unfair practice

I have a 36month contract with tracker, and my understanding is that both parties(tracker and myself) have to perform, they provide me a service and I pay my monthly fee in respect of a subject which here was my car which was fitted with a tracker. I was involved in a car accident where my car was written off meaning I no longer have a car and I am no long enjoying their services,there is no car to protect,and this is through no fault of my own,it is not like i have found a new company which has lesser premiums. So when I called them to cancel they than informed me that I will have to pay a settlement amount for the remainig period of my contract,I find it unreasonable and unfair under the circumstances.