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

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

Your phone suddenly shows "No service" or "SOS only", even though you are at home with good coverage and other people's phones work fine. Then emails arrive: "Your password has been changed", "New device logged in". This may be a SIM swap: a criminal has persuaded or tricked your mobile operator into moving your number to a SIM card they control. From that moment, calls and SMS meant for you, including one-time passwords, go to them. Speed matters: the first minutes count.

How does a SIM swap work?

1. They gather your details. Name, NRIC number, date of birth, address, sometimes your bank or email password, collected through phishing, data leaks or social media.
2. They impersonate you at your operator. With your details, and sometimes forged documents, they request a replacement SIM or eSIM from Singtel, StarHub, M1, SIMBA or another operator, claiming your phone was lost. In other cases they get help from an insider or trick you into approving a transfer.
3. Your SIM stops working. The moment the new SIM is activated, yours is cut off.
4. They take over your accounts. Using SMS codes, they reset passwords for email, social media, WhatsApp, and wherever your bank or other services still rely on SMS verification.

Many Singapore banks now use digital tokens in their apps rather than SMS OTPs for important actions, which makes a SIM swap less useful to criminals for banking. But your email, messaging apps and other services may still depend on SMS.

What are the warning signs?

• Sudden, unexplained loss of service on your phone while others nearby have signal.
• An SMS or email from your operator about a SIM change or eSIM transfer you did not request.
• Notifications of password resets, new logins or new devices on your accounts.
• Friends say they got strange messages from your number or WhatsApp.
• Unknown transactions in your bank account.

What do I do right now?

1. Contact your mobile operator immediately, from another phone or at a shop, using the number on its official website. Ask whether a SIM replacement or eSIM transfer was done on your line and, if so, to block it and give you back control.
2. Call your bank on the official number and tell them your phone number may be compromised. Ask them to monitor or freeze your accounts. Your bank's emergency "kill switch" can freeze accounts if you suspect unauthorised access.
3. Secure your email first, from a clean device: change the password and sign out of other sessions. Your email is the key to resetting everything else.
4. Check your Singpass. Review recent activity in the Singpass app and change your password if anything looks wrong. See Singpass for help.
5. Warn your contacts that messages from your number may not be from you.

What if money has already been taken?

1. Report it to your bank right away and ask about the transactions they can stop or dispute.
2. Collect evidence: the time you lost service, emails and SMS from your operator, and transaction details.
3. Make a police report through SPF e-services or at a Neighbourhood Police Centre. Your bank and operator may ask for the report number.
4. Follow ScamShield's I've been scammed checklist.

How do I stop it happening again?

• Ask your operator what extra security they offer for SIM replacement and account changes, such as a PIN or in-person verification.
• Move away from SMS codes: use an authenticator app, passkeys or in-app tokens wherever possible.
• Turn on WhatsApp two-step verification so your number alone is not enough.
• Do not share personal details like your NRIC number, date of birth and address with callers or on social media.
• Be wary of calls "from your telco" asking you to confirm details or approve a SIM change.
• Install the ScamShield app to filter scam calls and messages.

Frequently asked questions

My phone lost service but it was just a network outage. How do I know the difference? Check whether others on the same operator have service, and look for operator messages about a SIM change. If in doubt, contact your operator: it costs nothing to check.

Can they empty my bank account with just my number? Usually they need more, such as your login details too. That is why SIM swaps are often combined with phishing. Protect both.

I use an eSIM. Am I safe? eSIMs can also be transferred fraudulently. The same precautions apply.

Will my operator compensate me? That depends on the circumstances. Keep all evidence and raise it with the operator and your bank.

In short

Sudden loss of service plus security alerts means act now: call your operator from another phone, call your bank, secure your email and Singpass, and make a police report. Move away from SMS codes where you can. And if a suspicious caller tried to get your details, report the number in the NoCall spam numbers directory.