I once tried to get upgraded to J on LY using points, was told by the gate that I need to speak to the purser on board only he could do it.
When I arrived onboard I asked him and he told me no upgrades on points only for $750
So I started telling him that I have back issues... and need the upgrade, he said are you are not feeling well? you need to get off from the aircraft now we are not interested in making an emergency landing, I told him I'm fine, he was like are you sure will you make it to nyc... and I just ran to my seat and shut my mouth