If the dealer service damaged it, they should do what it takes to put the Mo back to the condition it was prior to their actions. Best bet is to insist on a new one. Even if the bumper is fine cosmetically, it was designed to absorb impacts through a collapsible foam under the bumper cover. If there was enough force to damage the outside, there was definitely damage to the inside. the dealer service should remove the bumper cover, ensure that all internals are undamaged or replaced and then put on a new bumper cover complete with matching paint.
Good luck.