You can set contacts alphabetically, but there is no setting to fix Favorites at the top. There is however, a separate Favorites page you can setup that is part of the phone app. When you open the phone app, look at the bottom of the screen and you will see several icons there, Favorites, Recents, Contacts, Keypad, and Voicemail. Instead of opening the Contacts, open Favorites. You can configure that page with those contacts you choose and also manually set the order they appear in on that page. To add a contact to the Favorites page, click on the + mark in the top right corner.