Your phone number receives sign-in codes, password resets and bank alerts. If a criminal moves it to their own SIM card, those messages go to them. A few free settings stop that, and protect the phone itself if it is lost or stolen.
About 12 minutes to read30 minutes to set upBeginner
1Why your number is a target
Many accounts trust your phone number as proof of who you are. That makes it valuable to criminals, who try to take it over in two main ways:
SIM swap: someone persuades or tricks your mobile carrier into moving your number onto a SIM card they control, often by pretending to be you with details found online.
Port-out: someone moves your number to a different carrier in your name.
Either way your phone suddenly loses service, and every text code and call now goes to them. With your email password or a reset link, they can then take over email, banking and crypto accounts within minutes.
Good news
Under rules adopted by the US Federal Communications Commission (FCC) in 2023, mobile carriers must verify your identity securely before moving your number, notify you of SIM change and transfer requests, and offer a free option to lock your account against both. You just have to turn it on.
2Lock your account with your carrier
This is the most important step in this module. Log in to your carrier's app or website as the account owner and turn on its protection. It is free, and often switched off by default.
Verizon
SIM Protection and Number LockSIM Protection blocks SIM changes; Number Lock blocks transfers to another carrier. Turn both on in the My Verizon app or website.
AT&T
Wireless Account LockPrevents your SIM or number being moved to another device or account. Turn it on in the myAT&T app or website.
T-Mobile
SIM swap and port-out protectionLook in your account's privacy and security settings. Only the primary account holder can change them.
Other carriers
Search “[carrier name] port out protection”All US carriers, including prepaid and budget brands, must offer a free lock. Call them if you cannot find it.
Also do this
Set an account PIN or passcode with your carrier that is not your birthday, address or the last digits of your phone number or Social Security number.
Give your carrier account a unique password and turn on two-step verification, using an authenticator app if offered.
Set a voicemail PIN that is not the default and not your number's last four digits. Some services can send sign-in codes by voice call to your voicemail.
Remember
When you need to switch carriers or phones, you will have to turn the lock off first, and some carriers add a short delay before changes go through. That small inconvenience is the protection working.
3Set a SIM PIN
A SIM PIN locks your SIM card whenever the phone restarts or the SIM is moved to another phone. Without it, a thief can take the SIM out of a locked phone, put it in their own, and receive your texts.
iPhone: Settings → Cellular (or Mobile Data) → SIM PIN.
Android: Settings → Security (sometimes under More security settings) → SIM card lock. Menus vary by manufacturer.
Before you start
You will be asked for the current SIM PIN, which is a default set by your carrier (look it up on their website). Do not guess: after three wrong attempts the SIM locks and you need a PUK code from your carrier to unlock it. Then change it to a new PIN of your own and store it in your password manager.
4Lock down the phone itself
A stolen unlocked phone gives a thief your texts, email and saved passwords. These settings make a stolen phone far less useful:
Do this
Use a 6-digit or longer passcode with Face ID, fingerprint or face unlock. Avoid simple patterns and 1234-style codes.
iPhone: turn on Stolen Device Protection (Settings → Face ID & Passcode). Away from familiar places, it requires Face ID or Touch ID for sensitive changes and adds a delay before your Apple Account password or passcode can be changed.
Android: open Google's theft protection settings (Settings → Google → All services → Theft protection on most phones) and turn on Theft Detection Lock, which locks the screen if the phone is snatched, and Identity Check, which requires your fingerprint or face for sensitive actions away from trusted places.
Make sure Find My (iPhone) or Find Hub (Android) is on, so you can locate, lock and erase a lost phone. Android phones can also be locked from any browser at android.com/lock.
Hide message previews on the lock screen, so sign-in codes cannot be read from a locked phone. iPhone: Settings → Notifications → Show Previews → When Unlocked. Android: Settings → Notifications → hide sensitive content on the lock screen.
5Depend less on text messages
The safest phone number is one that cannot unlock much on its own. Every account you move away from text-message codes is one less account a SIM swap can reach.
Switch your most important accounts to passkeys or an authenticator app, as covered in Module 1. Where the service allows it, remove the phone number as a sign-in method once another method is set up.
Keep your main number off public profiles, shopping sites and loyalty cards. A second number from a free calling app, or an email alias, is fine for sign-ups.
Be wary of anyone who asks for your carrier PIN or a code that was texted to you. Your carrier and your bank will never ask you to read those out.
6Warning signs and what to do
Signs your number may have been taken
Your phone suddenly shows No Service or SOS only where it normally works, while other people's phones are fine.
You get a message or email from your carrier about a SIM change, a new device or a number transfer you did not request.
You are suddenly signed out of accounts, or receive password reset emails you did not ask for.
Act fast
Contact your carrier immediately from another phone or computer, or visit a store with ID. Say you believe your number was moved fraudulently and ask them to restore it and lock the account.
From a safe device, change your email password and sign out of all other sessions.
Call your bank and card providers using the numbers on your cards, and check for unusual activity.
Change passwords on any account that uses your number for codes, starting with money, email and social media.
In the US, report it to the FCC and at reportfraud.ftc.gov, and consider a credit freeze if personal details may be exposed.
Check your understanding
What is the single most effective step against someone moving your number?
Your carrier's lock. A SIM swap happens at the carrier, so the protection has to be switched on there.
What does a SIM PIN protect against?
A thief using your SIM. Without the PIN, the SIM will not work in another phone or after a restart.
Your phone suddenly shows “SOS only” at home, where it always has signal. What should you do?
Act straight away. A sudden loss of service can be the only sign your number has been moved. Minutes matter.
Your checklist
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This module is general educational information, not professional advice, and following it cannot guarantee your number or accounts will not be compromised. Carrier and phone settings change and vary by model and country; follow your provider's current instructions. Products and carriers are named as examples only; Rondel Group is not affiliated with them.