Tim,
I use a Sprint PCS Vision Compact flash card in my Axim. It actually turns the Axim into a phone and it is also able to access Sprints Data Network. So you can use their wireless web, depending on where you live you can surf up to speeds of 144K. It is pretty sweet. I had this card in a laptop cruising up I-55 on my way to St. Louis and was surfing the net at that speed. The card I have cost about $230.00 and is compatible with Pocket PC 2002. The software just adds a phone interface to your handheld. It requires a earbud and mike, but that is all. Here is a link to the card I have at PC Connection, which is where I purchased mine:
http://www.pcconnection.com/scripts/produc...oduct_id=323798
Now since you already have a phone and don't want to spend anymore money you can get a card called a DPC that allows you to hook your cell right up to the handheld and your good to go. I have also provided a link to one of those too.
http://www.pcconnection.com/scripts/produc...oduct_id=241992
Hoped this helps!
Screen shot of Sprint PCS phone interface which I use