Tracker refusing to cancel a contract that they can't prove is still in contract.

This has been the most frustrating company to deal with. We have been disputing for 4 months that one of our fleet's trackers contract expired in Feb 2019. The vehicle was bought in Feb 2016 and a 3 year contract was entered into by the original company that purchased this bakkie. We purchased this vehicle in Oct 2018 and was told that the tracker expired in Feb 2019. I duly gave notice to cancel in March 2019, I was told then that Tracker believed this contract to expire in April 2020. I went back to the original company we purchased this vehicle from and they were adamant that this was incorrect, so I requested the signed contract which would prove who was correct. 4 months later and Tracker can't produce this contract but just keep dragging their feet on this matter whilst they continue to charge me. It is beyond frustrating and I'm really glad that our main contract is with CarTrack who are a joy to deal with in comparison.