My experience has been that the phone people will almost always recite the rules and tell you "no" and the gate people will almost always tell you "yes." I think the difference is legitimate and based on common sense...if the phone people start fudging the rules, then there is an issue at the airport and those seats are needed for others, the counter people have no leeway. If the plane is going to depart in ten minutes and the seats are STILL empty...then it's in nobody's best interest to tell you no.

I would echo the previous post that said go to the airport well before the flight you want (they always seem more willing when they aren't trying to check in a hundred other people who have reservations on that flight while you are asking for special favors), smile graciously, indicate that you know the one is nearly empty and couldn't they please do you a favor...but be prepared to graciously accept "no" for an answer, and smile and thank them for their time anyway. Anything less runs the risk of spoiling that agent forever to being nice to any of us....and I've actually had various people over the years in different settings change their minds and find a way do whatever I had asked, or something like it, BECAUSE I was gracious when they said they couldn't.