terms and conditions are different

i am stuck with my car because of battery and tracker told me that i changed my device and took the one with no road site and on the actual contract it has never said that anything like that. For the past three years was paying for the device and i was only tested twice and and called so many times to cancel and told it will be cancelled in three years and three years passed they continued charging me . Now am asking to cancel and they refuse to be told i must serve a notice . Dont understand because my contract is expired. I NEED THAT CONTRACT CANCELLED IN 24 HRS BECAUSE THEY ARE USELLES