Originally Posted by radonc1

I have never seen this happen on UA, but then again UA comps elites for UGs and almost always fills the domestic F cabin. However, when an E- passenger tries to auto-upgrade themselves to E+, the FA simply brings over the payment device and asks for the miscreants credit card . That generally produces an auto downgrade back to the original seat.
("I am surprised that AA FAs don't do the same thing).