Why Some Apps and Banks Reject Your Number (VoIP vs. Mobile Explained)

Some apps and banks look up what kind of line your number is on before they send a code. If it shows up as a VoIP number (an internet phone number), especially “non-fixed” VoIP that you can use from anywhere, some services turn it away to fight fraud. You can check your line type, use another way to verify, or use a number with a mobile carrier.

Below: the four line types in plain English, why companies reject some of them, how to check yours and what to do about it, all checked against FCC, FTC and company help pages in October 2026.

Mobile, landline, fixed VoIP and non-fixed VoIP in plain English

When an app checks your number, it’s usually trying to sort it into one of these groups:

Line type	What it means	Typical example
Mobile	A number from a mobile carrier, used on a phone with a SIM or eSIM	The number on a regular cell phone plan
Landline	A traditional wired phone line	A classic home or office phone
Fixed VoIP	Phone service over the internet, linked to a physical device at a location	A home phone that plugs into an internet or cable box
Non-fixed VoIP	Phone service over the internet that you can use from almost anywhere	A number you use through an app on your phone or computer

VoIP stands for Voice over Internet Protocol: your calls travel over an internet connection instead of a traditional phone line. The FCC notes that portable VoIP service can be used from virtually any internet connection.

The “fixed” and “non-fixed” labels come from the FCC’s 911 rules. The FCC describes fixed devices, like wired telephones, as ones you can’t readily move from one place to another. Non-fixed devices, also called mobile or nomadic, can readily be moved. That matters for emergencies: under the FCC’s 911 location rules, fixed VoIP providers must automatically send the caller’s location with every 911 call, while non-fixed VoIP providers must do so when it’s technically feasible.

Phone-number lookup companies use the same split. Twilio, which sells one of these lookup services, describes fixed VoIP as an internet phone number linked to a physical device, naming Comcast and Vonage as examples. It describes non-fixed VoIP as a number you can get online without any physical device, and names Google Voice as an example.

Why apps and banks reject a VoIP number

When you type your number into a sign-up or login screen, the company may check it with a lookup service before sending anything. Twilio says its lookup helps businesses screen phone numbers before they send a one-time passcode or create an account, and it lists blocking high-risk, non-fixed VoIP sign-ups among its main uses.

Here’s what a few companies say in their own help centers:

• Wells Fargo says it doesn’t currently support text messages to landline or VoIP phones and can only send texts to U.S.-based mobile numbers. It also uses texts to send one-time passcodes.
• OpenAI (the company behind ChatGPT) says it doesn’t accept landline, VoIP, Google Voice or premium numbers, because those types of numbers are often associated with more fraud or abuse.
• Google Voice itself says some websites, such as banks or subscription services, won’t send text messages to Google Voice numbers.

There’s a second, related snag: short codes. Some verification texts come from five- or six-digit numbers instead of a regular 10-digit number. Venmo, for example, sends its codes from a five-digit short code and suggests checking that your phone provider allows messages from short codes.

Each company sets its own rules, so a number that works for one app can be turned away by another. If your number is rejected, the error message is often your best clue.

How to check what type of line your number is on

1. Think about how you get service. A number that came with a mobile plan and lives on a SIM or eSIM in your phone is normally a mobile number. A home or office phone that plugs into an internet box or router is often fixed VoIP. A number you use through an app, with no SIM of its own, is often non-fixed VoIP.
2. Ask your provider. Your phone company can tell you what kind of service your number is on. The FCC also says to contact your provider if you’re unsure whether your service is VoIP that connects to the regular phone network.
3. Try a free carrier lookup. Search for “free carrier lookup” and you’ll find sites that show the company serving a number and how it’s labeled. Some only sort numbers into “wireless” or “landline,” and results are only as current as the site’s data, so double-check if the number was transferred recently. Skip any site that wants payment or promises an owner’s name and address.
4. Read the error message. Wording like “VoIP numbers are not supported” or “please use a mobile number” means the service checked the line type. A plain “invalid number” could mean the same thing, or just a typo or a missing country code.

How to fix a rejected VoIP number

1. Look for another way to verify. Check the sign-in screen or security settings for options such as a voice call, an email code, an authenticator app or a security key. The FTC’s guide to two-factor authentication says an authenticator app is safer than text codes because it isn’t exposed to SIM-swap attacks, and calls security keys the strongest method.
2. Contact the company. Use the phone number or chat on its official website or app, and ask what other verification options it offers for your account.
3. Use a mobile number for that account. If you also have a mobile plan, make that the verification number for the picky account, and keep your VoIP number for everything else.
4. Move your number to a mobile carrier. If you want to keep the number, you can transfer (port) it. The FCC says you can keep your number when switching between wireline, IP and wireless providers, as long as you stay in the same geographic area. Keep your old service active until the transfer is done, as the FCC’s porting guide advises. You’ll need the account number and transfer PIN from your current provider; see where to find your account number and transfer PIN and how to transfer your phone number to a new carrier. Moving a home line? Read can you port a landline number to a cell phone first.
5. Try again after the transfer. Once the transfer is complete, retry the app or bank. If it still says no, contact it and explain that the number is now with a mobile carrier. If codes simply aren’t arriving, work through our checklist for verification codes not received after switching carriers.

Protect your access before you switch numbers

If you plan to use a different number on your accounts, add the new number and confirm a code reaches it before you cancel the old one. Otherwise you could lock yourself out of an account that still sends codes to a number you no longer have. Where a service offers backup codes, save them somewhere safe.

Frequently Asked Questions

What’s the difference between fixed and non-fixed VoIP?
Fixed VoIP is linked to a physical device at a location, like a home phone that runs over your internet service. Non-fixed VoIP can be used from almost anywhere with an internet connection, often through an app. The FCC uses this split in its 911 rules, and lookup services use it to label numbers.

Is Google Voice a VoIP number?
Lookup services treat it as one: Twilio names Google Voice as an example of non-fixed VoIP. Google’s own help center says some websites, such as banks or subscription services, won’t send texts to Google Voice numbers.

Can a bank tell that I have a VoIP number?
It can check. Lookup services sort numbers into types such as mobile, landline, fixed VoIP and non-fixed VoIP. Wells Fargo, for example, says it doesn’t send text messages to landline or VoIP phones.

Will moving my number to a mobile carrier fix the problem?
It’s worth trying if you want to keep the number, since it will then be with a mobile carrier. Each company runs its own checks, though, so try again after the transfer is complete and contact the company if it still says no.

Are text message codes less safe than an authenticator app?
The FTC says an authenticator app is safer because its codes aren’t exposed to SIM-swap attacks, and security keys are the strongest option. If text codes are the only choice, the FTC says they’re better than nothing.

Why does WhatsApp say my U.S. number isn’t valid?
That error has a few possible causes. Our guide to the WhatsApp “not a valid number” error walks through the fixes.

Can I verify an account with a landline?
Sometimes. Look for a “call me” option on the verification screen. Some companies, such as Wells Fargo, don’t send text messages to landlines at all.

Looking for a number of your own?

212areacode.com has sold real U.S. phone numbers since 2009, mainly Manhattan 212 numbers plus numbers in many other area codes. After you buy one, you transfer it to your own carrier, so it rings on your own phone. Here’s how it works, or you can browse available numbers.