Risky experience

I recently bought a polo 2018 Trendline and put a tracker with cartrack on it, while trying to fix the paper of the vehicle, when I went to the garage I bought it at, the next day the previous owner of the car came to my work saying his tracker is still on. At that moment, I have my tracker with cartrack, he also has tracker on it with cartrack. Ever since that incident, I've been tailed several times, even had to take the car back to the garage because I fear for my life and safety now.

The main issue is, me and the previous owner used cartrack, couldn't there be a way to see that there is already a tracker of their company belonging to a different individual before they install a new one? And, since Thursday the 25th they said they'll call to arrange the de-installation, but I couldn't wait any longer because of being followed several times... I can't experiment with my life and health. As soon as I get whatever fee required, I see it best to terminate the contract, I'm cool with them. Couldn't they see the two trackers on the same vehicle beloning to different individuals, worse, from the same company? Like? What more can't they see or do? The guy saw me leaving the garage with the car, monitored my movements, and noticed I spend more time at work, and he came there, imagine. He could make a map on my movements and take the vehicle with peace, I don't know what he is capable of. This is a very risky experience, I wonder if other companies are likewise.