Took my car in to get an AC unit replaced and have...

Took my car in to get an AC unit replaced and have my engine checked out. After it was fixed they said all the bolts were tightened down to spec. I hear a rattling noise coming from my engine bay while checking my oil levels and I see one of my head bolts is busted from being over tightened. So much for being tightened to spec. I hope they can fix this problem since it was done at their shop.

UPDATE: Owner claims my last visit was over 2 years ago. Called to confirm it was less than 6 months. Owner lied.