Wirelessly posted (BlackBerry 8100: BlackBerry8100/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)

I am not sure really how it works to be honest. You might want to contact their support to find out if a data plan of some sorts is actually required in order for it to work. Or it might be in one of their manuals somewhere.