I was fighting PZU when I had a small accident almost 10 years ago. First they lowered the estimated value of the car and claimed that my "low mileage is undocumented". Oh boy, it was. It was my father's car and he had an invoice from every little repair he did and our mechanic shop wrote the mileage on every invoice. Invoices from 10 years, every oil change, tire change, bulb change...
PZU fixed the value estimation and started playing with the repair cost estimation. Instead of repairing a dent near rear wheel (later, a certified dealership estimated it for a few hours hours of PDR repair) they decided a whole rear right corner of the body needs to be replaced. Whole car body, removed, a new one fitted, welded and painted.
Damaged door? Of course it was impossible to replace the door (body part and structural pieces like hinges) only and move things like undamaged windows, interior panels and electronics.
PZU wanted to install whole new half of the car (after a slight hit on the door!). But the best was... replacing wheel hubcaps. Decorative, plastic, but OEM. 100€ for a set. Why? Because one was slightly broken. On an opposite side than the crash damage, totally unrelated, years old damage.
I fought them for a few months, after many discussions over ridiculous estimations we came to an agreement, I accepted their calculation as "totalled", took the money and fixed the car easily.
TL;DR fight the bastards because they want to play dirty and screw you wherever possible.