In reply to some earlier posts, you are beholden to the ground staff at the service desks/check-in.
On more than one occasion I have seen and complained about check in staff upgrading those not entitled to a higher class of travel or even uplifting staff with a lower travel category.
When staff travel works properly,it is a very good condition of employment.When it doesn't,I wish I had bought a full fare. But hey, that's the game.