The Three network has long been the go-to destination if you're looking for shedloads of data - it's still the only major player offering truly unlimited (and unrestricted) data packages. And time and again now it comes up with superb SIM only deals that we just have to shout about.
If you've landed on this page, we imagine you've already figured out that combining a SIM only plan with a SIM free phone or your beloved existing handset can be a brilliant way to save cash. And if it is big data that you crave, Three's £18 tariff for 30GB is unparalleled by the likes of Vodafone, EE or O2.
Scroll down to our comparison tool to pick out your ideal Three SIM only deal - whether you need it now, or to match up with a bargain handset. And if you're not yet sold on the Three network or are still unsure about how going SIM only works, keep scrolling down to our FAQ.
Is Three the best mobile network for me?
As we've said above, there are two very good reasons why you should consider Three for SIM only. The first is the price tag - it often gets the jump on the other 'Big 4' networks when it comes to its SIM card pricing. And the second is if you like a plan with oodles of data.
Plus, if you're looking for a network that's going to send freebies and rewards to your inbox every week, Three has just improved on that side of things, too. You get access to the Wuntu app, which gives you free coffees, cheap lunches and big discounts.
Three's Essential and Advanced plans
Grab a Three SIM, and you'll be on one of two plans:
Three Essential Plans
The cheapest Three SIM only deals are on the Essential plan, and this will be completely fine for most people. It lacks a handful of benefits that you get with Advanced, but you still get 4G coverage, unlimited texts and use of Wi-Fi on the London Underground. Unless you're a keen globetrotter or need to tether, stick to the bare Essentials.
Three Advanced Plans
Make the jump to an Advanced Plan and make yourself comfortable with the network's Feel At Home extra - unlimited use of your data, calls and texts in 60 other countries, including the US and Australia. Go Binge let's you stream Netflix, Apple Music TVPlayer, Deezer and SoundCloud away from Wi-Fi without eating into your data allowance. Plus, you can use your phone as a Personal Hotspot from which to tether your laptop or tablet.
Are Three SIM only deals cheaper than contract?
If you're at the end of your contract or blagged a friend's old unlocked phone, then grabbing a Three SIM card is undeniably cost effective. They start at less than £10 a month.
But if you're starting afresh with a new phone, you get no discernible benefit from heading down the handset and SIM only combo road with Three. Whether you're after an iPhone 8, Samsung Galaxy S8 or something cheaper, the deals you can get by simply grabbing a normal two year tariff are more reasonable in the long run. You can head to our mobile phone deals page to compare contract prices of the latest, greatest handsets around.
Can I keep my old number?
Give your current network a call (on one of the below numbers), ask for your PAC - short for Porting Authorisation Code - give it to Three and they'll gladly transfer over your old telephone number. So no need to send out a text to your entire contacts list with a new number:
- EE 07953 966 250
- O2 0344 8090202
- Vodafone 03333 040 191
- ID 0333 003 7777
- GiffGaff 43431 from your handset
- Virgin 0345 6000 789
- BT 0800 800 150
- Tesco 0345 301 4455
- Sky 03300 412 524
- Asda 0800 079 2732
Easy, right? But not so easy if you were already on Three and then decided to go for one of the deals in our comparison chart that isn't directly with Three. Three won't give you a PAC in this situation, so instead you'll have to grab the cheapest free pay-as-you-go SIM you can find from another network (e.g. O2, EE, iD, etc) and give them your PAC code from Three. Once your number has transferred to the substitute network, call them for a second PAC. Then you can give this to Three and continue using that same telephone number. A convoluted but handy workaround.
Is my phone unlocked - can I use a Three SIM in it?
If Three is where your heart is, then you may already know that it ships all of its phones completely unlocked. That means you can put a SIM card from any network in your handset and you're good to go.
Unfortunately, not all networks are as profligate in this regard. Some networks require you to pay to unlock your mobile and Apple iPhones are generally locked completely to the network they were originally sold with. Here's how the other major networks operate:
- EE Get through the first six months of your contract, call EE on 0800 956 6000 and pay them £8.99 and it'll unlock your phone. It says it will take around 10 days to complete. PAYG phones can be unlocked for free.
- O2 You can unlock any O2 phone for free if you're on a pay monthly contract. PAYG customers have to pay £15. That's unless your phone is a Samsung Galaxy S8 and S8 Plus, in which case you'll have to wait until the end of your contract before it can be unlocked.
- Vodafone Vodafone is similar to Three. It will unlock your handset for free, but you have to give them a call to do so. From there, it's likely to take 10 days before you can use another network's SIM in your phone.
What SIM card size do I need?
We hate to sound glib (we really do), but it doesn't really matter if you're moving to Three. Whatever plan you choose, you'll receive a 'trio-sim'. So whether your phone takes a micro SIM, nano SIM or an old-school standard SIM, you're covered.
What contract length should I get?
Three gives you the choice between signing up for a whole year, or paying a little more for 1 month at a time. It may cost you a few quid extra per month, but if you know that you'll only need use of your new SIM for a few months, it should save you plenty in the long run.
How much phone data do I need?
If you're sniffing around Three, there's a good chance that you've already made up your mind and want to go straight for the jugular - 30GB or unlimited data.
But if you're still trying to make up your mind, and have no notion of exactly how much data you'll really need per month, then our quick guide below will help. Alternatively, why not grab a big data deal for one month, see how much data you use, and then downsize after that...?
- 500MB-2GB If you just need a very cheap free SIM to shove in your phone and barely use data away from WI-FI, then we're not going to persuade you otherwise. But bear in mind that Three's 4GB tariffs can often be as cheap, or just a couple pounds more a month.
- 4-8GB This is a solid wedge of data that you should be able to bag for a reasonable monthly rate. A good amount if you want to safely use Google Maps, stream Spotify and update your downloads without going over your limit.
- 12-20GB Although unlimited data sounds very attractive on paper, ask yourself whether you really need it. And check your current usage - you may be surprised how far you can get with 12-20GB. It's a huge allowance that allows for loads of downloading, social media browsing and a few films' worth of streaming per month.
- 30GB At the risk of repeating ourselves, this is Three's sweet spot - whether you're going SIM only or contract. It's more data than most people will know what to do with, but the prices can be really reasonable. Far cheaper than going unlimited.
- Unlimited If you've already made up your mind about getting unlimited, we doubt there's much we can say to change your mind. And it's certainly a liberating feeling to have the freedom of unlimited data. But prices can get really expensive, so we'd urge you only to sign up if you really need it.
Should I get unlimited calls and texts?
Unlimited texts are a given with Three, regardless of whether you get an Essential or Advanced plan. But lots of plans do place restrictions on calls - usually 200 or 600 minutes. If you don't actually make that many calls from your mobile, then you can bag a cheaper deal by going for one of these. Chatterboxes should pay extra for unlimited minutes or, if you're going for a big data deal anyway, make use of apps like WhatsApp or the network's Three inTouch and use data calling.
How does TechRadar make money from SIM only deals?
If you buy a phone after visiting this page, TechRadar will be paid a small commission by the network or reseller you buy from. This money is paid by the site you buy from and thus does not affect the amount you pay for your phone contract. If you go direct to the site you buy from, you would pay the same amount.
While some sites out there will be paid larger fees for pushing people to specific deals that aren't necessarily the cheapest, TechRadar will always find you the absolute best value. Trust and integrity is important to us, so if you ever think we're not displaying the very best deals let us know.
If Three sounds like the network for you, then scroll back to the top of this page and select your SIM. rather try your luck elsewhere? Then head to our best SIM only deals guide for more information and the best prices from other networks.