Assuming you have the Blackberry Curve 3G, we need to perform a "register now" on your device.
From the home screen, hit the Blackberry menu button (the icon with the white dots).
Select options (the wrench icon).
Select "Advanced Options."
Select "Host Routing Table."
Once in the Host Routing Table, hit the Blackberry Menu Button.
Select "Register Now."
A popup will display "Registration Message sent!" - Select ok.
Once the above steps are complete, your phone may take a few minutes (5-10) to gain access to data. If not, you can pull the battery. If that does not work to resolve your issue, I would advise calling and speaking with tech support.