Best Three SIM-only deals in September

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Compare Three SIM-only deals

Three logo

If you're looking for a SIM-only deal, Three is a great choice. By grabbing one of its SIM plans, you can keep your phone (or buy a snazzy new one outright), and still get all the benefits of a Three deal. Plus, you're able to change your plan more often, so you always have the best possible SIM.

Compare deals

Three has something for everyone, whatever kind of SIM-only deal you need. Compare its plans right here with our mobile comparison tool - or keep reading to find out more about how to find the deal for you.

Is Three a good network?

Three is one of the biggest mobile networks in the UK, giving its customers straightforward mobile plans with none of the fuss and none of the expense of some rival household-name providers.

For SIM-only customers, it has an excellent choice of plans, with a little something to suit everyone – whether you want a small data allowance for a couple of months, or unlimited data for a couple of years at a good price.

There aren’t many big benefits or extras thrown in these days. But the upside of that is that you can enjoy low-cost monthly bills.

What SIM-only deals can I get from Three?

There are SIM-only plans for everyone with Three. You can choose between a 1-month, 12-month, or 24-month plan, with monthly data allowances ranging from 1GB to truly unlimited.

All come with unlimited texts, most have unlimited calls, and all are 5G-ready as standard.

As with most networks, longer-term SIM contracts are better value than the 1-month plans, if you’re willing to commit.

You can, of course, also grab a pay-as-you-go SIM.

What benefits does Three offer?

Three doesn’t offer much in the way of free stuff – such as the free entertainment app subscriptions you can get from EE, O2, and Vodafone.

Instead, Three focuses on offering you a good mobile phone service. So its benefits include:

  • Unrestricted mobile hotspot use
  • 5G at no extra cost (as long as your phone is compatible)
  • Go Roam, for no-cost roaming in 70 international destinations

Best Three SIM-only deals this week

Provider Data Amount Contract Length Monthly Costs
Three sim only Unlimited data 1 month £24.00
Three sim only Unlimited data 1 month £24.00
Three sim only Unlimited data 1 month £24.00
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile

Cheapest Three SIM-only deals this week

Provider Data Amount Contract Length Monthly Costs
Three sim only Unlimited data 1 month £24.00
Three sim only Unlimited data 1 month £24.00
Three sim only Unlimited data 1 month £24.00
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile

The cheapest SIM only contracts have lower allowances, are often on longer contract terms, and may be missing some of the features and extras of a more premium SIM plan. Existing customers can sometimes snag even better deals too.

To find the cheapest Three SIM option that suits you, just use our comparison table. Narrow the deals down with the filters, then use the 'sort by' toggle to order them by monthly cost. This will push the cheapest deals up to the top so you can see them first.

Best Three SIM-only deals with unlimited data

Provider Data Amount Contract Length Monthly Costs
Three sim only Unlimited data 1 month £24.00
Three sim only Unlimited data 1 month £24.00
Three sim only Unlimited data 1 month £24.00
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile
  • Three sim only
    5G
    • Unlimited 5G data
    • Unlimited minutes
    • Unlimited texts
    • download speed limit
    • £24.00 per month
    1 month contract From Three Mobile

Yes, you can get unlimited data from Three. Three has a small range of SIM deals with unlimited data, and you can grab one with unlimited calls and texts too.

Fair usage applies, but it's capped at 1000GB of data per month. You'll be hard pressed to reach that - it's ridiculously high - so it's really nothing to worry about.

How does Three SIM-only compare against other networks?

Of the big four mobile networks – Three, EE, O2, and Vodafone – Three generally tends to be the cheapest. It may not always be cheaper than smaller, budget networks or MVNOs (such as giffgaff or Tesco Mobile), but for what you get, it’s great value.

Coverage on Three is excellent, with 99% outdoor population reach. You should be able to get online wherever you are – but bear in mind its network isn’t the largest in the country. If you’re in a difficult-to-reach area, try EE instead.

It has a 5G network, but so far it isn’t as big as other networks’. Again, try EE if you’re keen to connect to 5G.

Not as many extras are included compared to other big networks. Three’s focus on offering a good, straightforward mobile service keeps costs down, but it does mean there’s no equivalent to O2 Priority or free streaming subscriptions.

Three used to be renowned for being the only network to offer unlimited data – but that’s no longer the case! You have plenty of choice of monthly allowance with Three SIM-only deals, and its spread of options is on par with other networks – including unlimited deals.

Alternative SIM-only networks to Three

Take a look at the different SIM-only packages and extras offered by mobile networks:

  • O2 - Customers get exclusive offers and vouchers for high street stores, restaurants and events through O2 Priority.
  • Vodafone - Enjoy entertainment subscriptions to Spotify, Prime Video and Sky Sports through Vodafone's Red Entertainment packages.
  • Giffgaff - Great value-for-money 30-day rolling SIM deals
  • EE - Six months of Apple Music for free and the best UK network coverage.
  • Smarty - Excellent value SIM-only plans with rewards each month for unused data
Frequently asked questions

What SIM-only deals can I get from Three?

There's a nice range of SIM deals available from Three, with options to suit all kinds of use. You'll find SIMs with small allowances for light users, all the way up to larger ones with lots of data, suitable for mobile fiends who use their phone a lot. Some plans come with a few other special benefits too - read more about those in our full guide to Three.

To see all the SIM-only deals available from Three right now, take a look at our comparison tool here:

How do I choose a Three SIM-only deal?

Finding the right Three SIM deal for you couldn't be easier. Have a look at the deals in our comparison table, and pick the one you like best.

You can adjust the filters at the side to only show the SIMs that fit what you need, and can even compare Three plans with those from other networks too. When you spot one you like, simply select it, and we'll take you straight to Three's website so you can order it.

When you're comparing, think about what's most important from your deal:

Data allowance - How much do you use 4G mobile internet? If you only use your phone to scroll through Facebook, browse the web a bit, and use WhatsApp, you'll be fine with a small allowance. On the other hand, hungrier users who stream on the go, use their phone for work, or download large files may want 10GB or so per month. Most of us, however, will find a data allowance between 2-5GB suits us perfectly.

Calls and texts allowance - Think about how much you make calls on your mobile, and how many SMS texts (not WhatsApp or Facebook messages) you send in a month. Very high allowances are available from Three for quite low prices, so getting enough for your use should be easy.

Contract length - With SIM plans, you usually have a choice between 30-day or 12-month contracts. Longer contracts generally have lower monthly costs, while a 30-day one can be changed at any time. It's worth going for a 12-month deal if you're happy to commit for a full year - though if you want a bit of flexibility, so you can change your monthly allowance or switch networks entirely whenever you like, go for a one-month SIM instead.

Price - On a budget? Set a maximum monthly price using the filter at the side, or sort all the deals by cost to see the lowest-priced ones first. See the section below if you need a bit of help finding the cheapest possible deal.

SIM card type - Make sure you get the right size SIM card for your phone. Most networks these days offer 'combi-SIMs' that can fit any device, so go for one of those if you're not sure.

Are Three SIM-only deals cheaper than contracts?

Yes, in most cases it's cheaper to go SIM-only than to take out a handset contract - partly because it means you won't be paying any interest or extra costs on the phone itself. Buying a phone outright and getting a SIM-only deal to put in it almost always works out cheaper in the long run.

As an extra price-saving bonus, SIM-only contracts usually last a much shorter length of time than ones with a phone… meaning you can switch to a new, even cheaper SIM as soon as you find one.

Can I keep my mobile number if I switch to a Three SIM-only deal?

Yep, you can keep your phone number when you switch mobile networks, regardless of which network you're switching to or from. It's surprisingly hassle-free to sort out, too.

All you need to do is sign up to a new deal, then contact your current network and ask for a PAC - a porting authorisation code. Give it to Three once you have your SIM, and the number should port across within a matter of days.

Do I need an unlocked phone to use a Three SIM?

Yes, your phone needs to be unlocked - or locked to Three - in order to use a Three SIM card.

If you bought your phone outright from a retailer, it should already be unlocked and you have nothing to worry about.

However, if you're using an old phone that you got on a contract, it may be locked to your former network. In that case, you'll need to get it unlocked - but don't worry, as this is easy enough to do.

All you have to do is contact the network it's locked to, and they'll sort it out - sometimes free of charge. They may give you a code to enter, or might be able to it remotely. Your phone will be unlocked and ready for a new SIM in a few days' time.

What size SIM card do I need?

There are four kinds of SIM card, sized to fit different devices:

  • Standard SIM - A classic full-size SIM, and the biggest of all. Generally only used in older phones, including old feature phones.
  • Micro SIM - A mid-size SIM, smaller than a standard one. Various phones from last few years take this size, including the Samsung Galaxy S5 and iPhone 4.
  • Nano SIM - The smallest SIM of all, and usually the SIM of choice for modern smartphones. This is the one you need for an iPhone 5 or newer, Samsung Galaxy S6 or newer, or a Google Pixel, for instance.
  • Combi-SIM - A clever three-in-one SIM. You can change the size of this SIM to make it fit in any phone. The majority of networks offer these as standard.

To find out what size SIM you need to get, take a look at your device's manual, or check the manufacturer's website.

If you're still not sure, don't worry - most networks send out combi-SIMs to make life easier.