Well, if they don't help you out, you can try at the airport. Once you've been checked in, I would imagine that the computer then views you as "flying." At that point you can say, "Well, I've now achieved Silver, according to the inanimate computer. May I use the lounge here?" They will probably be confused, but might let it go if you do it with a nice sense of humor.

If that doesn't work, there are always the more subtle methods:

1-threats
2-begging
3-crying