Leona, this is what I tried to do at the airport last December, but even though it took the money from my balance, the data didn't work.
Georgia...something else that I realized (after I lost my phone and had to buy another..lol) You need to make sure that you have followed the data setting instructions on the cheat sheet I sent to establish your APN (access point name). I got a new phone last week and thought it would "just work" with my old $$ and data when I had the SIM transferred. It did not, until I changed the settings and did the PREMIUM piece under APN.