Now...before i start, I've been a huge fan of Nextel for YEARS. In my opinion, best cellular provider out there. Especially for my needs, except for wireless data.
There are multiple plans that Nextel provides, allowing you to use your phone as a dialup modem. If i'm not mistaken, doing so does use your minutes. There might be like a monthly access rate where your minutes aren't subtracted from your account.
http://www.nextel.com, under services would probably get your more info than I really could.
Now, the nextel gods would probably cause my bill to double once this happens, but i do plan on aquiring a bluetooth phone and a bluetooth module for my Dell and i'll more than likely get T-Mobile's data plan. Unlimited access for 29.99 a month. In my opinion, that's gonna be the best deal for me. I plan to use my Axim often. Only thing that's gonna kill my hopes is if T-Mobile doesn't offer services here...I checked with Cingular, Verizon, and AT&T Wireless, and the winner, without a doubt, is T-Mobile.
http://www.t-mobile.com
check 'em out for more questions.