If you create a profile in 3G connections in Ubuntu (I’m currently using version 9.04), you will be able to connect but you won’t be able to reach any website, that’s because of a glitch in the default configuration for “Mobinil” service provider. To solve the problem:

1. Right-click on the Network Manager icon and choose “Edit Connections”
2. Choose the “Mobile Broadband” tab
3. Double click the “Mobinil” connection
4. Open the “IPV4 Settings”
5. In the “Method”, change from “Automatic (PPP) addresses only” to “Automatic (PPP)”.
6. Reconnect and enjoy 🙂