All of our toll-free numbers are voice-enabled by default. To add SMS functionality to a toll-free number, we need to validate the message content and your use case. Begin that process by filling out the Plivo Toll-Free Questionnaire form. After you submit it, our customer success team will validate your use case. If it's approved, you'll be able to search for and rent SMS-enabled toll-free phone numbers from the console or via the API.
You can read more about toll-free best practices and guidelines here.