Forced to pay for inactive tracker!!!

I bought my car in 2014 with beamie tracker already installed in my vehicle, then it happened that I changed a bank and it was never able to deduct their perimuims for a very long time. They contacted me and told me how much I owe and also told me the tracker is no longer active anymore in my vehicle and if I was continue with them I should inform them as soon after I have paid their outstanding money. I paid them the whole amount that I was owing them since it was my mistake and a year later they started phoning me telling me that I owe them for a tracker that it's not even active in my vehicle, they couldn't even locate where my car is when I asked them on the phone. The last time when I spoke to them I requested them to send me a proof that of whatever policy that I had signed for that says I will pay the tracker even if it's no longer active in my vehicle, since then they never contacted me again. But my only worry is that they have taken me to the lawyers and that will negatively affect my credit history.