I don't believe you can make reservations from that office; to do so, they'd have to access the website and be prepared for the mad rush days, and I just don't think they'd do that.
You could try 209-372-8502 which may get you through to that office, and ask.
Since you asked for ideas, if you can take a night off and go in to Oakhurst, spend the night at one of several motels with broadband internet access. If you don't have a laptop, the Days Inn at least has a couple of computers in the lobby (I suppose you'd want to get there early so someone isn't using it to chat 8^) Most of them will have reliable internet access there.
Or, you could drive to Yosemite Lodge and get internet access there from a laptop. Just be sure to check it first, their connection may need you to buy a day's access, or it may not and you can just connect. I'm not sure I'd trust their connection though, if it's a really important trip.
They're pretty reasonabe in February; $50-60 seems like it would be worth it instead of canceling your February trip.
Gary
Yosemite Photo Galleries: http://www.pbase.com/roberthouse/yo