VoIP number
Google Voice, TextNow, and browser-based SMS receivers fail the carrier lookup outright, regardless of which country they claim.
AI Tool Won't Accept Your Phone Number? Here's the Fix
How-to — — by Mahmoud Zalt
Fix a rejected phone number on an AI tool signup: understand carrier lookup, avoid VoIP numbers like Google Voice, and get the SMS code to arrive.
The fastest fix: get a number, or a platform, that clears the check
You've probably already tried the workaround: a Google Voice number, a free TextNow line, or a friend's mobile number from a country your account isn't even registered in. All three tend to fail the same way. The field either rejects the number outright, or the code gets requested and simply never shows up in your messages.
Here's the part most troubleshooting guides skip: a real mobile number from a supported country clears this check immediately, no trick required. If you'd rather sidestep phone verification entirely, that option exists too. Sistava's signup only asks for an email and a password, there's no phone number field on the form at all, so a blocked SMS check on one AI tool never has to be the reason you can't get an AI Employee working today.
Why does the AI tool reject your phone number?
The rejection usually happens before your phone ever buzzes. Most signup flows run a carrier lookup the instant you submit the number, a real-time check against telecom data that returns the line type, the carrier, and the country tied to it. If that check comes back as VoIP, unregistered, or mismatched to your account's country, the code simply never gets sent.
That lookup sorts numbers into a handful of types: mobile, landline, fixed VoIP like a Google Voice number tied to an address, and non-fixed VoIP like TextNow or a browser-based SMS receiver. Only the mobile category reliably passes, because it's the one type the lookup can confirm is a real, carrier-registered SIM. A landline can't receive SMS at all, and both VoIP categories score as higher fraud risk no matter which country they claim.
OpenAI states this plainly for ChatGPT: landlines, Google Voice, and other VoIP or premium number types aren't supported for phone verification, specifically because that category has a long history of abuse. That's not one vendor being difficult, most major AI platforms run the same carrier-level check for the same reason. The number itself is what fails the test, not your account or anything you did wrong on the form.
Benefits
Country mismatch
A real mobile number registered in a different country than your billing address or account region can fail the same check.
Recycled or aggregator number
Numbers bought in bulk from resale services share known prefixes that fraud databases already flag.
Landline
Can't receive SMS at all. Some forms let you submit one anyway, right up until the lookup catches it.
What actually gets a code delivered?
A real mobile number, on a plan with an actual carrier, from a country the platform supports. That's the whole answer, and it's boring on purpose. Everything else, VPNs, disposable-number apps, a relative's number from abroad, is a workaround chasing a check that a normal phone plan passes without any extra step.
A few edge cases are worth naming honestly. An eSIM from a legitimate travel-SIM provider usually reads as a real mobile number and passes, because it's issued by an actual carrier rather than routed over the internet. A colleague's or family member's number will work technically, but it ties the account's identity to a number you don't control, which causes its own problems the moment you need to recover access. Reputable paid virtual-number services built for verification, not the free disposable kind, sit in between: they can work, but they're the last resort here, not the first move.
The safe sequence to fix a rejected number
- Confirm it's actually a phone-verification block — Read the exact error text. "Not supported for this account type" or "invalid number" points at line type, not your country generally.
- Try your own mobile carrier number first — Most rejections resolve here. A postpaid or prepaid SIM from a real carrier is the number type every platform's lookup is built to accept.
- Match the number's country to your account country — If you signed up with a US billing address, a mobile number from another country can still fail even though it's a real SIM.
- Check if the platform needs phone verification at all — Some, including Sistava, only ask for email and password. Confirm before spending time hunting for a compliant number.
- Contact support with the exact error, last resort — If a genuine carrier-registered number still fails, support can usually confirm whether it's a known issue or manually clear the flag.
| Number type | Passes verification? | Why |
|---|---|---|
| Mobile, carrier-registered | Usually yes | Confirmed real SIM tied to a carrier the lookup recognizes |
| Fixed VoIP (Google Voice) | Usually no | Tied to an address, not a SIM, flagged by line-type detection |
| Non-fixed VoIP (TextNow, browser SMS) | Almost always no | No carrier registration at all, the top source of abuse |
| Landline | No | Can't receive SMS regardless of policy |
| Legitimate eSIM (travel/local) | Usually yes | Issued by a real carrier, reads as mobile in the lookup |
None of this is arbitrary once you see the mechanics. The strictness makes more sense once you know what it's actually defending against, which is the part most people never get told.
Why are platforms this strict about a phone number?
Free-tier AI accounts are a magnet for bulk abuse: scraping, spam generation, and reselling access to accounts created faster than a human could sign up. A phone number is one of the cheapest signals a platform has to slow that down, because a real SIM costs money and takes a carrier relationship, while a VoIP number can be generated by the thousand for nearly nothing.
The scale is real, not theoretical. Research tracking disposable-number usage has found millions of one-time verification codes sent to temporary numbers across major platforms, well beyond a handful of bad actors testing the system. That volume is exactly what a carrier lookup exists to filter before it ever reaches a human review queue.
There's also a direct cost angle: every SMS a platform sends costs money, and bots that request codes on a loop without ever completing signup can run up real charges, sometimes called SMS pumping fraud. Rejecting VoIP and mismatched numbers before the message goes out isn't just about who gets in, it's about not paying to text a number that was never going to become a real user.
If you're evaluating a few AI platforms at once, the phone-verification step is a decent early signal on its own. A tool that gates you behind SMS the moment you land is optimizing for abuse prevention over friction, which is a reasonable trade for them and an annoying one for you. A tool that skips it entirely isn't cutting corners, it's just made a different bet about who its signups are.
Either way, the fix for a rejected number is never a VPN or a fake billing address, both of those solve the wrong problem and put the account at risk later. Fix the number type first, the country match second, and only reach for support once both check out.
Frequently asked questions
FAQ
Why does my AI tool keep rejecting my phone number?
Almost always because of the number's line type, not your account. Signup forms run a carrier lookup the instant you submit a number, and it returns whether that number is a real mobile SIM, a landline, or VoIP. VoIP numbers, including Google Voice and free apps like TextNow, get flagged automatically because that category is heavily associated with bulk fake signups. Switching to a real mobile number from a carrier you actually pay for resolves the vast majority of these rejections.
Why do Google Voice and TextNow numbers get rejected specifically?
Google Voice is a fixed VoIP number tied to an address rather than a SIM card, and TextNow is a non-fixed VoIP app, neither is issued by a mobile carrier the lookup can confirm. Both categories are cheap or free to generate in bulk, which is exactly the abuse pattern platforms are trying to filter. OpenAI states this explicitly in its own signup guidance for ChatGPT, and most major AI platforms apply the same rule even when they don't publish it as clearly.
The verification code never arrives even though the number looks valid. What's happening?
The lookup runs before the SMS is sent, so if it flags the number as VoIP, unregistered, or mismatched to your account's country, no message ever goes out, there's nothing wrong with your phone or your signal. Check the account country you selected against the number's actual country first. If those already match and it's a genuine mobile SIM, the next step is contacting support with the exact number and error, since a small share of rejections are false positives on the carrier's side.
Can I sign up for an AI tool without giving a phone number at all?
Yes, on platforms that don't require it. Sistava's signup only asks for an email address and a password, there's no phone field anywhere in the form. Some mainstream AI chat tools do require phone verification on their free tier specifically as an anti-abuse measure, so if avoiding it matters to you, check the signup form itself rather than assuming every AI tool works the same way.
Will using a family member's or colleague's phone number work?
It usually passes the carrier check, since it's a real mobile SIM, but it creates a different problem later. Account recovery, security alerts, and any future re-verification will route to a number you don't control, which becomes a real headache the day you actually need it. If you have any other option, a number you personally control is worth the extra effort now.
Does an eSIM or travel SIM count as VoIP?
Generally no, if it's issued by an actual mobile carrier rather than routed purely over the internet. A legitimate eSIM from a travel-SIM provider reads as a normal mobile number in a carrier lookup and typically passes verification the same way a physical SIM would. The exception is an eSIM reseller that's actually reselling VoIP capacity under the eSIM label, which is harder to spot from the outside and worth checking the provider's own documentation for.
Is it safe to use a paid virtual-number service for verification?
It depends on the service and how you use it. A reputable paid provider built specifically for legitimate SMS verification is a real, narrow fix when you genuinely lack a mobile number, unlike the free disposable-number apps that fail the same lookup a VoIP number does. The line not to cross is using one to misrepresent your billing country after the fact, that's the part that creates account risk later, not the verification itself.
Is a rejected phone number the same thing as a country block?
No, and the fix is different for each. A country block rejects everyone from a country outright, no number would work. A phone-verification rejection is about the specific number's line type or its mismatch with your account, and a different, compliant number from the same country usually clears it immediately. If you're not sure which one you're facing, try a real mobile number from your own country first, if that still fails, you're likely looking at a country block instead.
Why did a number that used to work suddenly stop passing verification?
Carrier lookup databases update continuously as VoIP providers get identified and added to the flagged list, so a number that passed a year ago can start failing without anything on your end changing. Ported numbers can also briefly misreport their carrier during the porting process. If a previously working number starts failing, waiting a day or two before troubleshooting further rules out a temporary database sync issue.
A rejected phone number feels personal, especially after the second or third attempt, but the mechanics behind it are almost never about you. It's a carrier lookup checking whether the number in the field is a real, carrier-registered SIM from a country that matches your account, and everything else follows from that one check.
If phone verification keeps getting in the way of testing a new AI tool at all, it's worth stepping back and picking a platform whose onboarding doesn't gate you behind SMS in the first place. The next read covers the wider version of that problem, what to do when a whole AI SaaS tool, not just its signup form, decides your region isn't supported.
Keep it simple: a real mobile number, matched to the country on your account, clears almost every phone-verification rejection on the first try. Save the workarounds, VPNs, and disposable-number apps for a problem they're actually built to solve, because this one usually isn't it.