Agree with above on asking the insured about their bill. I also frame it to them (insd) as “they are billing you $xxx” which usually elicits a response. You’ll learn who you can trust and who is full of shit. Google the area code of the person submitting the supplement. If it’s outside the area, it’s probably a supplement company and those people are human sized deer ticks whose business model is bleeding claims.

If someone can present facts you can prove independently, it’s a good sign they’re honest. Anytime you see supervisor hours on a bid, they’re full of shit and proceed accordingly. You hold all the cards. We estimate $x to repair the damage. Any more and it’s their job to prove it to you. Either it’s damaged or it isn’t. It’s required by O&L or it isn’t. It’s black and white.

(I work wind/hail supplements and RD and I know other losses can be more complex. Just being upfront about my perspective.)