Rear facia crooked after fender bender

My car got rear ended a few weeks ago and I had it professionally repaired at a GM dealership. I didnt notice it at the time, but the rear facia was crooked since the repair. Me and my freind removed the rear facia today and found that the mounting bracket on the right side is still damaged from the wreck.

So I am a little bit angry that they didnt fix this when I brought it in to be fixed, and now I am sure they will charge me for another repair.

Anyways, is there a way to replace this bracket myself or do I have to take it to a dealer ship? It looks like the brackets are riveted on which is a pain.