Cartrack service very poor

During July/August 2020 I contacted cartrack to come and remove their device from my car and put it into a new car I bought, the old car was still with me for two weeks and I requested them to do this in this two weeks. Nobody form cartrack ever came back to me. I struggled with them for a very long time until such time I decided to stop paying cartrack and that's when I got a reaction from them when they didn't receive payment any more. So now two years later they gave me up at law firm for collection, I don't have any tracking device installed in my car and did not get any services from them for two years. They say I did not honnor the contract with them but they are the ones who failed to honnor their side of the contract. Even when the device was in my X-Trail I reported to them to put the device in revice mode as my car was at a mechanic to repair the engine. They cobtacted me one evening at past 12:00 to tell me there is tampering with the battery while the battery was removed three days prior to their call for the mechanics removed the engine. In other word their service to me was utterly poor close to non existent.