How to Use Internet In BLACKBERRY without A blackberry Plan

Go to Menu > options > Advanced Options > TCP/IP

Check the box "APN Settings Enabled" and Write The APN (Access Point Name)

Save the options and now you can use any third-party applications like opera, whatsapp, logicmail etc.

Note:
1. APN will be different based on your country and carrier.
2. You can't use blackberry apps with this method. (e.g. bb browser, bbm, appworld etc.)