Louisiana General Contractors - Ever served a "notice to owner?"

My buddy did a kitchen remodel job a few weeks back and hasn't gotten paid and the job has been completed for at least a week. They owe him about 2K and have refused to pay because they want him to remove some tile that he put as a backsplash and think he should remove and replace it for free. What sayeth the OT? Also, they picked out the tile and it was laid properly. I personally think they don't have the money to pay.