Phishing7 min readPublished 14 July 2026 · Updated 21 September 2026
SIM Swap Fraud: How Criminals Hijack Your Phone Number
SIM swap fraud allows criminals to take over your phone number and bypass two-factor authentication. Learn how it works and how to protect your accounts.
A sudden loss of mobile service, followed by password-reset alerts or banking messages you did not request, can be a sign that someone is trying to take control of your number. Treat the loss of service as an account-security incident, not merely a network fault.
How SIM Swap Fraud Works
The attack begins with the fraudster gathering personal information about the victim — often through phishing, data breaches, or social media research. Armed with enough details (name, date of birth, address, and sometimes the last four digits of the victim's National Insurance number), they contact the victim's mobile network and impersonate them.
They claim the victim's SIM card has been lost or damaged and request that the number be transferred to a new SIM card they control. Once the transfer is complete, all calls and texts — including bank verification codes — go to the fraudster's phone.
What Happens Next
With control of the phone number, the fraudster uses the "forgot password" function on banking apps and email accounts. The verification code is sent to the hijacked number, and within minutes, accounts are accessed and funds transferred.
Warning Signs Your SIM Has Been Swapped
- Your phone suddenly loses signal and shows "No Service" or "SOS Only"
- You stop receiving calls and texts unexpectedly
- You receive a notification about a SIM change you did not request
- You cannot log into accounts that use SMS two-factor authentication
How to Protect Yourself
| Protection | How It Helps |
|---|---|
| Use an authenticator app | Not vulnerable to SIM swap (unlike SMS codes) |
| Set a SIM PIN with your network | Prevents unauthorised SIM changes |
| Limit personal info on social media | Reduces information available to fraudsters |
| Use a strong, unique email password | Harder to access even with your phone number |
| Enable account alerts | Immediate notification of suspicious activity |
What to Do If It Happens
Contact your mobile network immediately to report the suspected SIM swap and regain control of your number. Then contact your bank and any other important service that uses SMS authentication. Report suspected fraud through Report Fraud.
Check the contact while securing the account
Check suspicious links or numbers in ScammersCheck from a trusted connection, but prioritise contacting your mobile provider and bank through official channels. A technical result cannot tell you whether your SIM has been swapped or restore access to an account.
Source note: Call and message safety steps are informed by Ofcom guidance and reporting through Report Fraud. Use app-based authentication where a service supports it.
Received unexpected verification codes or lost phone signal suddenly? Check the associated phone number or email with ScammersCheck.
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