bad service

I had a reinstallation for my car tracker and they took it out and installed it in my new vehicle. the following day i called to tell them that something is wrong my car and the owner of my old car also complained that the technician left his car with lots of lights on while he fixed the car the previous day. so i have complained since august 2021 send emails Whatsapp calls no response but now they threaten me with blacklisting and summons. the technician blocked me