I can also check mine on T-mo's site. Not sure about Rogers though. It wouldn't hurt to see if they offer the service on thier site. I can check minutes used on my Berry, but not data... so far anyway. Do you know how much data your plan covers? If it is around 500 mb, then it will be difficult for you to surpass that without using your BB as a modem.
Posted from my CrackBerry at wapforums.crackberry.com