SIM swap: my phone suddenly lost service, what do I do?

You're at home, at work or out on the street, somewhere you always have signal, and suddenly your phone shows "No service" or "Emergency calls only". You restart it and nothing changes. The person next to you has signal just fine. It might be an outage, but it might also be what's known as SIM swapping, or a fraudulent duplicate SIM: someone has convinced your mobile carrier to activate your number on another card (or an eSIM), and from that moment they receive your calls and, above all, your texts with banking codes. In this situation minutes matter, and there is a specific order in which to act.

How does a SIM swap work?

The fraud almost never starts on the day you lose service. It usually has three stages:

1. They collect your details. Through a fake text or email from your bank, a call pretending to be tech support, or data leaked in other breaches, they get your name, ID number, phone number and, often, your online banking credentials.
2. They impersonate you to your carrier. With that data, sometimes with a forged document, they request a replacement SIM or an eSIM activation, claiming the phone was lost or stolen, in a shop, over the phone or through the customer account area.
3. They use your number to get into your accounts. When the new SIM is activated, yours stops working. Now they receive the verification codes by text and can authorise transfers, add cards to a phone wallet, change your email passwords or take over your WhatsApp.

That's why they often strike outside business hours or at weekends: they're counting on you taking hours to notice.

What are the warning signs?

• You suddenly lose signal in a place where you always have it, and restarting the phone doesn't fix it.
• Shortly before, you got a text or email from your carrier about a SIM change, an eSIM activation or a change of details you didn't ask for.
• You receive alerts from your bank or email about new sign-ins, password changes or a new device.
• WhatsApp logs you out with a message saying your number has been registered on another phone.
• A few days earlier you got a text or call "from your bank" asking for details or passwords, and you gave them.

A single sign on its own doesn't prove anything. Losing service plus any alert about changes to your accounts is reason enough to act now.

What do I do right now?

Follow this order. You'll need another phone (a relative's, a colleague's or a landline) or internet access over wifi.

1. Call your carrier from another phone. Use the official customer service number from its website or your bill, never one sent to you by text. Ask whether a replacement SIM or eSIM has been issued for your line. If so, ask them to block that SIM immediately and record that the request was fraudulent.
2. Call your bank on its official number. The one on the back of your card or on its website. Explain that you suspect a SIM swap and ask them to block online banking, cards and transfers while it's sorted out. If you bank with several institutions, call all of them.
3. Take back your email. From a computer or tablet on wifi, change the password of your main email account: it's the key to resetting every other account. Sign out of all sessions and check they haven't added automatic forwarding or a new recovery phone number.
4. Check your transactions. Log in to online banking (if you still can) or ask the bank for recent transactions, new virtual cards and authorised devices. Take screenshots of anything you don't recognise.
5. Warn your contacts. If they've taken your WhatsApp, they may ask your family for money pretending to be you. A message from another account or a phone call is enough: "My number has been stolen, if I message you asking for money, it's not me."
6. Keep the evidence. Note the time you lost service, take screenshots of the alert texts and emails, and write down the names of the people you spoke to at the carrier and the bank.

Don't wait to "see if the signal comes back". Every minute the criminal controls your number is a minute in which they can receive verification codes.

What if money has already been taken?

It's not your fault: this fraud exploits weaknesses in identity checks that don't depend on you.

1. Ask your bank in writing to record the transactions as unauthorised and request a refund. Payments you didn't authorise give you the right to claim, and the sooner you report them, the better.
2. Report it to the police. In Spain, to the Policía Nacional (091) or the Guardia Civil (062), at a station, with all your evidence; elsewhere, to your national or local police. Bring the time you lost service, the alerts you received, the bank transactions and the carrier's confirmation that a replacement SIM was issued. Your bank and carrier will ask for a copy of the police report.
3. Complain to your carrier for issuing the replacement without verifying your identity. Ask them in writing for details of when, where and how it was requested.
4. If you need guidance: in Spain, call INCIBE's 017, the free and confidential cybersecurity helpline, and see the OSI (Spain's Internet User Security Office) guides on recovering accounts; elsewhere, contact your national cybersecurity agency or fraud helpline.

If you feel you're in danger or someone is threatening you, call 112 (or your local emergency number).

For details on how to claim your money back, see how to recover money lost to a phone scam.

How do I stop it happening again?

• Don't use text messages as your second factor when there's an alternative: an authenticator app or a security key doesn't depend on your SIM.
• Set a PIN on your SIM and ask your carrier whether you can add a password or extra verification for changes to your line.
• Never share personal details or passwords by phone or text, even if it looks like your bank. Your bank will never ask you for codes or passwords. If in doubt, see how to check whether a call or text from your bank is real.
• Turn on notifications from your bank and email so you hear about any change instantly.
• An app like NoCall helps you spot the fraudulent texts and calls that these attacks usually start with, before you hand over your details.

Frequently asked questions

Could it just be an outage? Yes. Network outages happen. But if you're somewhere you normally have signal, other people on the same carrier have service, and you're also getting alerts about changes to your accounts, treat it as fraud until your carrier tells you otherwise. Calling to check takes five minutes.

Will I get my number back? Yes. The carrier can cancel the fraudulent SIM and issue a new one to you after verifying your identity. Your number is still yours.

I have an eSIM, can this happen to me too? Yes. The fraud can consist of activating an eSIM on another device. The signs and the steps are the same.

What about WhatsApp? Once you get your line back, register WhatsApp again with your number: the verification code will come to you and the criminal will lose access. Then turn on two-step verification with a PIN.

In short

If you suddenly lose service with no explanation, act as if it's a SIM swap: call your carrier and your bank from another phone, take back your email, warn your contacts, keep evidence and report it. If a number that contacted you earlier asking for details looks suspicious, report it in NoCall's spam number directory: it could be the first piece of this fraud for the next person.