OpenAI Phone Number Not Supported? How to Bypass the Block
Getting the "Phone number not supported" or "This number cannot be used" error on OpenAI or Anthropic developer platforms? Here is the technical explanation and a direct fix.
Written by Robert Brock
Founder & Telecoms Specialist • Updated June 2026
Why OpenAI Rejects Your Phone Number
OpenAI employs Arkose Labs and specialized risk gateways during developer signup to protect their API servers from automated sybil attacks and bot setups. During the verification step, OpenAI does not just check if a number can receive an SMS—it queries the authoritative carrier network databases in real-time.
The Real-Time HLR Lookup Mechanics
When you type your number, the gateway performs an HLR (Home Location Register) lookup. This query checks the MNC (Mobile Network Code) and MCC (Mobile Country Code). If the lookup flags the number as a "virtual/VoIP routing block" (used by VoIP apps like Google Voice, OpenPhone, Skype, or Twilio), the system automatically triggers a PHONE_TYPE_UNSUPPORTED response, rejecting your account.
Because virtual/VoIP numbers are cheap, scalable, and disposable, platforms use blanket bans on them. Standard prepaid numbers are also frequently blocked because they carry high spam risk flags in global telecom databases.
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How to Bypass the OpenAI Phone Block
1
Identify Your Number's Classification
Identify Your Number's Classification
Use our free VoIP Verification Checker to verify if your number is registered as a virtual VoIP block or a native mobile network. If it is classified as virtual, OpenAI will reject it under all circumstances.
2
Obtain a Native eSIM Number
Obtain a Native eSIM Number
Select a carrier-native provider like SecondSim. SecondSim is not a virtual number app—we provision genuine physical mobile lines on standard Tier-1 carrier networks. Because our numbers are registered in the GSMA database with a standard Mobile Network Code (MNC), they are recognized as physical SIM cards, passing OpenAI’s automated fraud filters.
3
Disable Your VPN and Use Incognito Mode
Disable Your VPN and Use Incognito Mode
If OpenAI has previously blocked a registration attempt from your IP address, your browser session and IP are likely flagged. Turn off any VPN or proxy services, open an incognito browser window, and clear your site cookies before attempting verification with your new eSIM number.
Comparison: Number Eligibility for Developer Portals
| Number Provider Type | OpenAI / Anthropic Status | Verification Method | Carrier Database Flag |
|---|---|---|---|
| VoIP (Google Voice, Skype) | ❌ Always Blocked | SMS / Call | Landline/Software Spoofed |
| Twilio / Plivo APIs | ❌ Always Blocked | SMS / Call API | A2P Virtual Gateway |
| Disposable SMS Sites | ❌ High Risk Flag | Public Web Inbox | Shared Number Range |
| SecondSim eSIM | ✅ 100% Passes | Native SIM / DSDS | Tier-1 Mobile MNC |
Frequently Asked Questions
Can I reuse a phone number for multiple OpenAI accounts?
No. OpenAI restricts each verified phone number to a maximum of 2 individual API or ChatGPT accounts. If you try to verify a third account, you will receive an error stating the number has been used too many times. You must use a fresh, native mobile number.
Why did my verification work on WhatsApp but fail on OpenAI?
OpenAI's gatekeeper, Arkose Labs, has a higher fraud sensitivity setting than Meta's general verification. While some premium VoIP providers occasionally slip through WhatsApp's filters, OpenAI uses real-time MNC verification sweeps that intercept virtual numbers immediately.
Can I verify an account with an eSIM if I'm not in the UK?
Yes. SecondSim eSIM profiles can be activated on any compatible smartphone globally. Because our numbers route incoming SMS over standard carrier roaming networks, you will receive the verification code instantly regardless of your physical location, and OpenAI will recognize the number as a legitimate UK mobile endpoint.