TL;DR: Which? warned in August 2026 about calls impersonating Three, claiming your number will stop working within 24 hours or your SIM will be blocked, to extract personal and payment details. Similar calls and texts use O2, EE and Vodafone. The goal is often your account access, which can lead to SIM swaps or phones ordered on your contract. Hang up and check in your network’s app or by calling the number on your bill. Report by texting “call” and the number to 7726.

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The call

Which? reported on August 28, 2026 that callers claiming to be from Three say your number will stop working within 24 hours or your SIM will be blocked. They ask for personal and payment details to “keep it active.”

It’s a close cousin of O2’s inactive SIM text, and the same script turns up with EE and Vodafone branding.

What they’re really after

Why your phone account is worth stealing

Cifas’s Fraudscape report, published in May 2025, found unauthorised SIM swaps rose 1,055% in 2024, with nearly 3,000 cases filed to the National Fraud Database. 48% of account takeover cases involved mobile phone accounts, unauthorised mobile upgrades rose 96%, and people aged 61 and over made up 29% of account takeover victims.

Which? reported in April 2026 on victims who lost around £3,000 to £3,500 after SIM swaps, including one Vodafone customer who waited 10 days to get her number back. Ofcom told Which? networks would consider customers’ location before allowing email-based swaps.

How to check

Report it

Text “call” followed by the number to 7726 (on Android, text “call” and follow the prompts), as Which? advises. See how 7726 works.

If you shared details

Call your network immediately and ask them to check for upgrades, SIM changes or porting requests, and add a password or PIN to your account. If your own phone has lost signal, contact the network by webchat or from another device, as Which? advises, and call your banks to freeze accounts. If your phone loses signal unexpectedly, act fast: how to block a swapped SIM. Tell your bank too, or dial 159.

Lock your account before anyone calls

Which?’s advice: use a strong password and two-factor authentication on your mobile account, ask your network for an extra PIN or password for sensitive changes, protect your email (fraudsters have used email access to request swaps), and prefer passkeys over SMS codes where you can. Keep your date of birth off public social media profiles.

Scammers often already know your name and number from leaks. A free email exposure check shows what’s circulating about your email.

Frequently Asked Questions

How common is SIM swap fraud in the UK?

Cifas recorded a 1,055% rise in unauthorised SIM swaps in 2024, with nearly 3,000 cases. Mobile accounts were involved in 48% of account takeover cases.

How do I protect my mobile account?

Use a strong password and two-factor authentication, ask your network for an extra PIN for changes, and secure your email account.

Will Three block my SIM within 24 hours by phone?

Treat such calls as scams. Check in the Three app or by calling the number on your bill.

What do fake mobile network callers want?

Payment details, or account access that can be used for SIM swaps or ordering phones on your account.

How do I report a scam call in the UK?

Text "call" followed by the number to 7726.

What should I do if I gave a code to a caller?

Call your network immediately to check for SIM changes and orders, and add an account PIN.

Sources

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