Hi,
Security Pro does not have an SMS option for Two-Factor Authentication. With Security Pro, you can use choose from email, mobile app (such as Google Authenticator and Authy) or use a one-time backup code that is provided upon setup.
If you have an account with iThemes, you can enter a support ticket through the link below. Please keep in mind that iThemes is only able to assist the account owner with issues.
https://members.ithemes.com/panel/helpdesk.php
Thanks,
Matt