One place to start would be the connections setup. Go to Settings and tap on the Connections tab, then tap on the Connections icon. Once that opens tap on the Advanced tab at the bottom. On that screen tap on the Select Networks button. Tap on the Edit button under the first pull-down and on the next screen you can click on New and it will step you through entering the the parameters for a new network. To set it up the APN is blackberry.net, the username is rim, and the password is password.
No guarantee that any apps that normally run over Media Net will work over it though. Pocket IE won't, but that is the only one I've tested.