Or you could always get an upgrade the normal way, by going onto the website and paying for it.
That's a horribly cynical perspective on someone who's just trying to be friendly!
Reminds me of one of my female check-in clerks who was confronted by a particularly smarmy man, reeking of aftershave, clinking with gold chains, and thinking he was God's gift to humanity and women in particular. He leaned over and whispered in her ear : "Tell me my darling, what do I have to do for you to get an upgrade?".
Without even looking up, and without a nanosecond's hesitation, she simply said : "Go to the ticket counter and pay for it."
I was standing behind, picked up his ticket, and walked him over to the ticket counter where he was deeply embarassed, admitting that he'd been trying to get a free upgrade.