Keeping Your Number: Porting, SIM Swaps and How to Protect Both
The same process that lets you take your number to a new carrier can, in the wrong hands, move it away from you. A few settings make the difference.
What number porting is
Number portability lets you keep an existing telephone number when you switch from one provider to another. For mobile lines it is often called mobile number portability. It exists so that changing carrier does not mean telling everyone a new number.
How a normal port works
- You sign up with the new carrier and ask to bring your number.
- You provide details that prove the line is yours, often including an account number and a transfer PIN or code from the old carrier.
- The carriers coordinate the move. There may be a short period when calls or texts do not arrive.
- Your old plan with that number ends; check whether any final bill or device payment remains.
Do not cancel the old plan before the port completes. Cancelling first can release the number, and then there is nothing to move.
What a SIM swap scam is
A SIM swap scam is a type of account takeover in which a criminal convinces or tricks a carrier into moving your number to a SIM card they control. Once they have it, texts and calls meant for you, including login codes, go to them. An unauthorised port to another carrier has the same effect.
Warning signs
- Your phone suddenly shows no service in a place where it normally works.
- You receive a message about a SIM change or port request you did not make.
- Friends say they texted you and you never saw it.
- You get password-reset emails you did not request.
If several of these happen together, contact your carrier from another phone immediately.
Protect the number
- Ask your carrier for an account PIN, port-out protection or a number lock if they offer it.
- Keep your carrier account login strong and protected with two-step login.
- Limit how much personal detail you post publicly; it is often used to answer security questions.
Protect the accounts behind the number
The deeper fix is making your number less valuable. Move important accounts from text-message codes to an authenticator app or security key, as explained in the one-time passwords guide, and remove the phone number as a recovery option where a stronger option exists.
eSIMs change the steps, not the risk
An eSIM is a SIM built into the device and programmed remotely rather than a removable card. Moving an eSIM to a new phone still goes through the carrier, so the same protections apply.
Write down your carrier's account PIN or port code somewhere safe. You will need it when you genuinely switch, and nobody who calls you should ever ask for it.