Fitted lights and extraction fan in the wrong plac...

Fitted lights and extraction fan in the wrong place, even though it was clearly marked with an X marks the spot. My builder had to rectify their work.
Fitted new light switched in the bathroom and toilet which were coming of the walls by 3mm. Not safe at all, so also had to be fixed.
All 3 new installed lights flicker constantly. They refused to come back to check what the problem is. Instead they chased me for payment and threatened to send their invoice to a collection agency. I paid their invoice but will have to get another company out to fix all their work.