Short answer
In a SIM swap, a scammer persuades your mobile carrier to move your number to a SIM they control, then receives your calls and verification texts. The first sign is usually that your phone suddenly loses service, or you get a notice that your SIM was activated on another device. Contact your carrier immediately from another phone to get the number back, then change your passwords — email first — and check bank and card accounts. Afterwards, ask the carrier for a PIN or password on your account and move important logins from text codes to an authenticator app, security key or passkey.
Signs it’s happening
- No service, no texts and no calls — out of nowhere.
- A message that your SIM or number was activated on a new device.
- Password reset or sign-in emails you didn’t request.
What to do in the first hour
- Call your carrier from another phone and say your number may have been hijacked.
- Once the number is back, change your email password first, then banking and social accounts.
- Sign out unknown sessions everywhere: who else is logged in?
- Check bank, card and payment accounts for charges or changes and report them.
Lock it down
- Set a PIN or password on your mobile account; ask about a port-out or SIM-change lock.
- Replace text-message codes with an authenticator app, a security key or a passkey: passkeys explained.
- Post less personal data publicly — it’s used to answer security questions.
What carriers must do (US)
In the US, FCC rules adopted in 2023 require carriers to use secure ways to verify a customer before moving a number to a new device or carrier, to notify customers of SIM-change and port-out requests and to offer account locks. Port-out fraud — moving your number to another carrier — is the same attack in a different form.
Report it
In the US, report the scam at ReportFraud.ftc.gov, and use IdentityTheft.gov if personal or financial data was taken. Elsewhere: report online fraud by country. For locked-out accounts: lost two-factor access, WhatsApp hacked. Our hacked account recovery service works through official channels.
Frequently asked questions
What is a SIM swap?
A scammer gets your carrier to move your phone number to a SIM they control, so they receive your calls and verification texts.
What is the first sign of a SIM swap?
Usually your phone suddenly loses service — no data, texts or calls — or you get a notice that your SIM was activated on another device.
How do I stop a SIM swap?
Set a PIN or password on your mobile account, ask for a SIM-change or port-out lock, and use an authenticator app or passkey instead of text codes.
Does an eSIM prevent SIM swapping?
It removes the physical card, but the FCC notes that port-out scams remain a risk.
Sources: FTC — SIM swap scams: how to protect yourself, FTC — what to do if you were scammed, FCC — cell phone fraud, FCC — rules to protect consumers’ cell phone accounts (2023), FCC — eSIM cards FAQ