It depends on what type of Blackberry device you have. You will need to perform a handheld wipe on the device. Performing this procedure disables all data services (web browsing, email, etc.) and removes all data (passwords, contacts, etc.) from the handheld. Here are some general steps how to perform a handheld wipe.
- From the Home screen, press the Menu button.
- Select Options.
- Select Security Options.
- Select Security Wipe.
- Ensure that the desired options are selected, enter blackberry into the Enter to confirm device wipe field then select Wipe.
A 
indicates that the option is selected. - Emails, Contacts, etc. -All application data will be erased.
- User Installed Applications -All user installed applications will be erased.
- Media Card -All data on the Media Card will be erased.
