GPS tracker shorted out OnStar radio and door locks and they will not pay to have it fixed

I bought a used vehicle and they modified it with a GPS tracker on it. however the way they installed and wired it into the electrical system shorted out the OnStar, the stereo , and the door locks. When they added the tracker and installed improperly are they liable to repair those functions due to the fact that they 1 if an accident occurs OnStar can not notify the police or the ambulance service. 2 the OnStar runs through the stereo system. 3 the door locks are hard to unlock because they got real small knobs to grab. What can I do if anything or is it only hypothetical or conjecture if something bad that could have been when their device shorted out the security features of the car.