If your cell phone suddenly loses service and shows "No Service" or "SOS only," it may not be a bad signal. It can be the first sign that a criminal has taken over your phone number.

This is called a port-out scam. It is quiet, it happens fast, and it can open the door to your bank, email and investment accounts. The good news: a few simple steps make it much harder to pull off, and acting quickly limits the damage if it does happen.

What is a port-out scam?

A port-out scam happens when a criminal moves your phone number to a new carrier or device they control, without your permission. From that moment, your calls and text messages go to them instead of you.

Moving a number between carriers is called "porting," and it's a normal service. It's what lets you keep your number when you switch providers. Scammers abuse that same process.

You may also hear about SIM swap scams. They work the same way, except the criminal convinces your current carrier to move your number to a new SIM card they hold. Either way, the result is the same: someone else controls your phone number.

How the scam works

Most port-out scams follow the same pattern:

  1. The criminal gathers your details. To move a number, they usually need your name, phone number, carrier account number and transfer PIN. They may find these in data breaches, through phishing texts or emails, on social media, or by calling you while pretending to be your phone company.
  2. They open service with a new carrier. Posing as you, they sign up with a different provider and ask to bring "your" number over.
  3. Your number moves. If the details match, your current carrier releases the number. Your phone loses service, often with no warning.
  4. They intercept your codes. Any verification code sent to your number by text or phone call now goes to them.
  5. They go after your accounts. With those codes, they can reset passwords, sign in to your bank or email, pose as you on the phone, or apply for credit in your name.

This can all happen quickly, sometimes before you realize anything is wrong. That's why noticing the warning signs early matters so much.

Why your phone number is so valuable to criminals

Your phone number has quietly become one of the keys to your financial life. Many banks, email providers and apps use it to:

  • Send one-time verification codes when you sign in
  • Let you reset a forgotten password
  • Confirm it's really you when you call customer service

When a criminal controls your number, they can pass all of these checks. They don't need to know your password if they can simply reset it. That's what makes a port-out scam so dangerous: it's rarely the end goal. It's the first step toward your bank accounts, investments, email and credit.

Warning signs

Watch for any of these, especially more than one at a time:

  • Your phone suddenly loses service and shows "No Service" or "SOS only" while others nearby have signal
  • You get a text or email from your carrier about a port-out request or SIM change you didn't make
  • Someone calls claiming to be your phone company and says your service is being "upgraded," "migrated" or "transferred," then asks for your PIN, account number or a code
  • You receive a welcome message or bill from a carrier you never signed up with
  • You get password reset or login alerts for accounts you didn't try to access
  • Your bank or email locks you out without explanation

In November 2023, the Federal Communications Commission adopted rules requiring wireless carriers to authenticate customers before moving a number and to notify customers right away when a port-out or SIM change is requested (FCC). So take any unexpected notice from your carrier seriously.

How to protect yourself

A few small steps make your number much harder to steal:

  1. Add a port-out PIN or number lock. Call your carrier using the number on your bill or its official website, and ask what protections they offer. Many carriers let you set a separate transfer PIN or lock your number so it can't be moved without extra verification.
  2. Never share codes or PINs with someone who contacts you. Your real carrier won't call out of the blue and ask for your PIN, account password or a verification code. If someone does, hang up and call the number on your bill.
  3. Use stronger sign-in protection. Where your bank and email allow it, switch from text-message codes to an authenticator app or a passkey (more on this below).
  4. Ask your bank for an extra layer. Some banks offer a verbal password or will flag your account so large transfers are confirmed another way.
  5. Limit what you share online. Your phone number, birthday, address and carrier details all help a scammer pass as you.
  6. Use unique passwords. A password manager makes this easier, so one breach doesn't unlock everything.

What to do if it happens to you

Act quickly, and work through these in order. Use another phone, a landline or a trusted family member's phone if yours isn't working.

Right away

  • Call your carrier. Use the number on your bill or the carrier's official website, never a search ad. Ask whether your number was ported or your SIM changed. If so, ask them to restore it and add a port-out PIN or number lock. If your number was moved to a new carrier, contact that carrier's fraud department too.
  • Call your bank and investment firms. Use the number on the back of your card or statement. Ask them to flag your accounts, hold or review outgoing transfers, and stop using your phone number to verify you until it's restored.
  • Secure your email. Change your password, check that the recovery phone and email are yours, and sign out of all other devices.

Within a few days

Is two-step verification still safe?

Yes, keep using it. Two-step verification (also called multi-factor authentication, or MFA) still blocks many attacks. The weak point in a port-out scam isn't MFA itself, it's the type: codes sent by text or phone call depend on your phone number, and a number can be stolen.

port-out-table

A text-message code is still much better than a password alone. But for your bank, investment and email accounts, switch to an authenticator app or passkey wherever it's offered.

How Carefull helps

Carefull is built to catch the warning signs that follow a stolen phone number, and to help you recover.

  • Money Monitoring: Link your bank accounts, credit cards, and investment accounts in Carefull. The AI runs a 2-year lookback on your transaction history to build a profile of what's normal for you, then alerts you to anything outside your usual patterns — with a focus on scams, fraud, and everyday money mistakes like missed bills or duplicate charges.
  • Credit Monitoring: Credit Monitoring is powered by Iris (through Equifax) and continuously watches your credit report for changes — new accounts, hard inquiries, delinquencies, address changes, fraud alerts — and sends you real-time notifications when something happens. Activating it also automatically sets up an SSN monitor for you.
  • Hack Recovery: Open the Hack Recovery tool inside your Carefull account. It gives you a detailed list of areas to address — reminders to update passwords or add extra security measures on other accounts outside of Carefull.
  • ScamCheck: Not sure if a call, text or email is really from your phone company? Paste the text, upload a screenshot, or forward the message, and get a clear "scam / not a scam" answer with next steps. If it's unclear, you can talk to a real Carefull fraud specialist.

The bottom line

If your phone suddenly stops working, don't assume it's just a bad signal. Call your carrier using a number you trust, then check in with your bank. Add a port-out PIN today, and move your most important accounts off text-message codes. A few minutes now can save weeks of cleanup later.