Three £18 unlimited data SIM only: get the exclusive deal
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Save £120 against the full price of unlimited data on Three. We show you how to get it and all the pros and cons of the offer. Last updated: 10th July 2025.
What's the deal?
Unlimited calls, texts and data for £18 (4/5 deal rating)
At the time of writing, this exclusive Three offer is the cheapest unlimited everything deal on a main UK network. Its full price on the main Three website is £28 per month, so you’ll save £120 over a year.
You’ll also get the usual Three benefits of the fastest 5G in the country, 99% 4G coverage, WiFi calling and their reward app - all on a 12-month contract. And shortly, some extra coverage via Vodafone too.
Useful link: Our full Three review
What's good about it?
It’s truly unlimited data, for your phone
There’s always a bit of doubt around whether unlimited data is truly unlimited. But we’re confident saying Three’s plan is. You can tether, there are no speed caps, and no traffic management (throttling).
Just bear in mind that their unlimited SIMs are designed solely for personal use on your phone. Three do run checks to detect usage in routers or dongles. They will block SIMs that are being misused.
They also monitor usage above a massive 1000GB per month. That’s not a hard cap. You can go past it. But it's the point where they’ll double-check you’re genuinely using it in a phone, not another device.
Almost no normal user will ever get near that anyway. So we don’t consider it a real restriction.
Useful link: Read Three's terms and conditions
Unlimited data on the UK’s fastest 5G network
Three have a great network to use unlimited data on. Their network has always been optimised for heavy data users. They carry the most data in the UK. Independent testing shows their 5G is typically the fastest in the UK.
They’ve also come a long way with 4G. Huge investment has gone into upgrading their masts and converting old 3G into faster, more reliable 4G. Check your local signal here.
And if you join Three today, you will slowly benefit from more and more coverage through Vodafone. The two companies have merged and are now in the process of combining their networks.
Useful link: Check Three signal in your area
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