Over charge for 2 cars which is device was installed in one car

In 2023 l have joined car tracker for 2 cars but one was installed in one car the other one was not installed but they are charging one 2 cars l have been asking them to stop changing me now they handed the account to Nimble to do collection no help l got from them. They send me a message that l have a discount while they handing my account to Nimble group. Cartracker is a ****