Ok.....
How about having them check your credentials on the FAA website?
https://www.faa.gov/licenses_certificates/airmen_certification/interactive_airmen_inquiry/
I’m hoping they’re doing a little more of a background check then just eyeballing your plastic certificate card?
Best example I can find on short notice
If your certificate does NOT state SIC priviliges only then it’s a PIC type rating.
The ‘powers that be’ that you are trying to convince should know that.