Why OpenAI & WhatsApp Block Virtual Numbers (And How Non-VoIP Verification Works)

A developer explains why platforms like OpenAI and WhatsApp block virtual phone numbers, detailing how carrier lookup APIs such as Telesign and Twilio Lookup identify VoIP lines in real-time. The post highlights that physical Non-VoIP carrier SIMs are required for successful verification.

When developing, testing, or signing up for modern platforms like OpenAI ChatGPT , WhatsApp Business , Google , or Telegram , you have likely encountered these frustrating errors: ⚠️ "OpenAI services are not available for this phone number." ⚠️"This phone number cannot be used for verification." ⚠️"Virtual phone numbers VoIP are not supported." Why do these errors happen even if you use numbers from popular providers like Google Voice, TextNow, or standard Twilio virtual numbers? In this post, let's explore how modern authentication systems detect virtual lines and why physical Non-VoIP carrier SIMs are required. When you enter a phone number on a modern web platform, the backend verification engine queries a Carrier Lookup API e.g., Telesign, Twilio Lookup, or Neustar in real-time before sending the SMS. These lookup APIs return metadata about the number: json { "country code": "US", "phone number": "+1XXXXXXXXXX", "carrier": { "name": "Bandwidth.com / Google Voice", "type": "voip" } }