Device not working, Cartrack keep asking me for money

My tracking device has been inactive for months. An agent called me and told me it's inactive and that I would have to pay a call out fee for a technician to fix it. I told the agent I was not prepared to pay this fee, I would rather cancel. Cartrack keep asking me to give them a 21 days notice for cancellation. My question is, why give notice when I'm not getting services. None of them are able to answer this question, but instead they tell me I have to agree to this in order to cancel. I am not prepared to give 21 days notice on a device that doesn't work, and I am not prepared to pay for services I'm not getting.