look very closely from all angles

feel on it for bumps

if you see bumps, high or low spots, or even color mismatch then you can refuse the work and request a do-over.

the bumps are caused by inferior prep work and failure to keep the area clean before they apply primer or paint

high or low spots are when the area that has been repaired appears to be higher or lower than other areas, this comes from use of too much or too little coats of primer or paint

well color mismatch is obvious if the color doesn't match then don't pay for it (and don't let them tell you it will get darker the more time it has to dry this is a trade lie) they should never try to return a car to you that has not had the proper time to dry