How we fixed the "Invalid Mobile Number" error for WhatsApp Verification
If you have tried to register a WhatsApp Business account recently using a virtual number, you have likely hit a wall.
We noticed a significant spike in support tickets last month from users getting the error: "This number is not a valid mobile number." After digging into the carrier logs, we realized that Meta has quietly updated their security protocols to aggressively block VoIP (Voice over IP) ranges.
The Problem: VoIP vs. Real Carrier Lines Most SMS verification tools resell numbers from providers like Twilio or Bandwidth. While these are great for standard notifications, they are registered as "virtual" lines. WhatsApp now performs a real-time carrier lookup (HLR check) during registration. If the number flags as virtual, the OTP is never sent.
The Solution: Server-Side Physical SIM Routing To solve this, I completely restructured how LegitSMS handles WhatsApp requests.
We just deployed a new dedicated server specifically for this use case. Instead of generating virtual numbers, this server routes requests through a pool of physical SIM cards (Non-VoIP) connected to our gateway.
Why this matters for your privacy:
Bypass the "VoIP Block": Because these numbers originate from real mobile carriers (like Vodafone, T-Mobile, etc.), they pass the HLR check instantly.
Privacy Protection: You can verify a WhatsApp Business account to separate your work/personal life without needing to buy a second hardware phone or contract.
Instant Delivery: By filtering out the "bad" VoIP numbers, our success rate for OTP delivery has jumped to nearly 99%.
How to test it: If you have been stuck in the "Invalid Number" loop, we have opened up this specific server for public access.
Go to the WhatsApp Verification Page.
Select your country (US, UK, and Netherlands are currently the most stable).
Use the number to verify your account.
This update is live now. I’d love to hear your feedback on the delivery speeds! 🚀
