I have cell phone service through Verizon, but it should work just the same with Sprint. I use a Samsung phone A640, and an mobile office kit I got at the Verizon store. All it is is a USB cable that plugs into the phone on one end and the computer on the other. I use JUNO for dial-up access. Software comes with the cable kit to let your computer reconize the phone as a modem. Just plug it in, and use your dial-up access just like you were connected to a phone line. BUT!! IT IS SLOW!!!! 14.4 with acceleration still is only 23.0 baud, about 1/3 the speed of your home line. It is OK for receiving e-mail, no pictures if possible, a little bit of internet slowly. The only problem with JUNO is that they have a lot of handshaking to you conputer when it connects, and you have to wait for it to finish. I would recommend one of the bare bones dial-ups rather than AOL or JUNO. Earthlink might be OK, I have never used them myself.
Hope this helps, my account has free nights and weekends, so I can use all the minutes I want to after 9:00 and on weekends. There is no additional charge for data service either, although I have found a few locations where the service is not supported. West Virginia in particular. Also, cell phone access is limited in the boondocks.