Car tracker bad service

I have the contract with car tracker in 2018 March.after sometimes in june 2019 i started to experience that my units is no longer working after i had a car accident and my battery was removed from the car for 25days.when i call car tracker to came and fix the units they never come.from june until September 2019 when i decides to cancel my contract with them.now they ara busy telling me that i must pay them even after i cancelled the contract with them.they told me that i must pay them for the service and when i ask them that how would i pay for something that is cancelled they said is how the work.but i am not going to pay for something that i never borrow.they treated me like am nothing to them.bad service i ever received.