Hidden Auto Antenna GPS Tracking Device In Car HELP!?

GPS tracking device in car HELP!? - hidden auto antenna

I am aware that a GPS tracking device (no phone) in my car. May the key of my secret and put them in, but do not know. 1) How do I know if this thing lies? 2) a way to disable it. Where can I get help to find this thing? Is a regular repair shop find for him? Help me please. Privacy totally penetrated.
PS This thing has no antenna. The size of the battery. Spark Nano think.