Took my car to get the side light fixed cause I bo...

Took my car to get the side light fixed cause I bought it like that and they waited for the part went to get the car to find this damage on it. They said it was like this before but i don't know how when as you can see there is no scratch on the mirror nothing can cause this damage other than someone working on it not even blind side warning works and it worked before I got there and they're trying to convince me it was there before. Now they don't want to fix what they broke.
Edit: I tried calling to come in but they wouldn't call back to schedule something with me to see it this is what I got.. on the pic. They said this is clear lol. Went up there on Saturday only assistant manager worked said I understand but I cant help you. ALWAYS take pictures of your car before going here...