If your not getting results from the shop that painted the car, and the work was done on an insurance claim, contact the ins co. and tell them your not happy with the results from the shop. The ins co's carry more weight with getting a shop to complete the job to your satisfaction. I've known people who's Ins Co sent the car out for re-painting at a different shop at their expense.
But if you took the car in at your own expense, the shop knows they can usually get by with what they are doing to you.