1. Power the phone on. The phone should go through the basic start-up and come to rest on the main screen.
2. Press the "Menu" button and find the "Settings" option, then "Reset Settings." You may have a "Restore Factory Settings" option here, or a more extensive menu that lets you choose what to reset, such as sound settings, display settings, phone settings or all.
3. Reset the phone by choosing "All" or "Restore Factory Settings." Press the "Yes" button when the phone asks you to confirm that you want to reset it.
4. Power cycle the phone, and when it comes back on you will be able to reconfigure your settings correctly.