Your phone number is the backup key to a surprising number of accounts. Banks, email providers and social apps text you a code when you log in or reset a password. That makes your number a target: in a SIM swap, a scammer talks or tricks your carrier into moving your number to a SIM card or phone they control. In port-out fraud, they transfer it to a different carrier. Either way, your texts and calls start going to them.
The FCC adopted rules in 2023 requiring carriers to verify customers more securely before moving a number and to notify you when someone requests a SIM change or port-out. But the three big U.S. carriers also offer free locks you can switch on yourself.
Verizon: SIM Protection and Number Lock
Verizon has two separate switches. SIM Protection blocks SIM changes, upgrades and bring-your-own-device activations. Number Lock stops anyone from generating the transfer PIN needed to move your number to another carrier.
- Open the My Verizon app and tap the Me tab.
- Tap Edit profile and settings, then scroll to Security.
- Tap SIM Protection, switch it on for each line and tap Confirm.
- Go back to Security, tap Number Lock and switch it on for each line.
AT&T: Wireless Account Lock
AT&T uses one free lock for the whole wireless account. It blocks SIM and eSIM swaps, upgrades, number transfers, adding or removing lines and changes to billing details. Paying your bill and changing your plan still work. Only people with primary or secondary access to the account can turn it on.
- Open the AT&T app on a phone that’s active on your account and sign in.
- Tap the person icon, then Wireless account lock.
- Swipe to lock.
T-Mobile: SIM Protection and Port Out Protection
On postpaid plans, T-Mobile’s SIM Protection stops your number from being moved to another device. Port Out Protection, which is also free, blocks transfers to another carrier and has to be added line by line.
- In the T-Life app, open Manage, tap the gear icon, then Security > SIM Protection. Switch it on, tap Save Changes, then Continue.
- For Port Out Protection, go to Manage > See Plans > Manage add-ons, pick a line, check Port Out Protection, then tap Continue and Agree & Submit. Repeat for each line.
Prepaid customers use a different menu on T-Mobile’s website, and only the primary account holder can remove either lock.
Two Things to Remember
- Unlock before you upgrade or switch. These locks block legitimate changes too. Turn them off before buying a new phone, moving to eSIM or changing carriers. Verizon notes that SIM changes stay blocked for about 15 minutes after you disable SIM Protection.
- Don’t rely on text codes for your most important accounts. The FTC recommends an authenticator app or a security key instead, because a text code won’t help you if someone has your number. A passkey is even better where it’s offered.
If your phone suddenly loses service and you get a notice that your SIM was activated somewhere else, call your carrier right away from another phone. Then change your passwords, check your financial accounts and, if personal data was taken, follow the steps at IdentityTheft.gov.
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