Here is a neutral and interesting 1-paragraph summary of the text: When enrolling new users, it's essential to focus on three key areas: phone number input, validation, and verification. Best practices for phone number input include keeping country codes separate and transforming numbers into E.164 format, while also checking IP geolocation against the country code for potential correlations with fraudulent activity. Phone number validation involves using the Twilio Lookup API to confirm validity, detect line types, build allow lists of countries, and maintain carrier information based on reputation. Finally, phone verification requires sending one-time passcodes to verified numbers, building retry buffers into workflows, and keeping phone numbers visible in enrollment flows to prevent typos. By following these best practices, businesses can reduce fraudulent sign-ups, improve user experience, and enhance overall security.