car giving issues after unit installation

I've been experiencing turn signal issues immediately after the unit was fitted on my car and now they won't work at all. I wrote the email to the fleet department to explain to them about the situation I'm experiencing since the unit was fitted but no one has bothered to come back to me and I hear that this is where they are best at....keeping silent and ignoring complaints. everything was working fine until their technicians worked on the car. now I'm risking my life driving a car that doesn't indicate when changing lanes.