The best unlimited data SIM in 2024, based on our annual customer survey and full mobile network reviews
Sick of running out of data? These are the best unlimited data SIM plans as determined by our survey of thousands of customers
The best unlimited data SIM plans from the top mobile networks will give you peace of mind when you’re scrolling through the news on the train, running along to Spotify or finding the perfect restaurant on holiday. Slot one into your phone and you will never be caught short, but which one should you pick?
You shouldn’t simply buy the first unlimited data SIM you come across: there are lots of important factors to keep in mind, including the length of the contract, value for money, performance, coverage and whether the price includes any extras.
To help, I’ve put together a list of the best unlimited data SIM-only deals based on the results of the latest Expert Reviews Mobile Network Awards survey, which had over 4,000 respondents. And, if you’re not sure where to start, I’ve also compiled a handy buying guide that answers the most important questions. Surf’s up.
Best unlimited data SIM: At a glance
| Best deal | Smarty | View deal at Smarty |
| Best for speed | EE | View deal at EE |
| Best for calling abroad | Lebara | View deal at Lebara |
The best unlimited data SIMs you can buy in 2024
1. Smarty: The best unlimited data SIM deal
Price: £20/mth | View deal at Smarty
Pros
Smarty may have been usurped by Voxi in our latest Mobile Network Awards, but it still finished in second place overall and remains the best unlimited data SIM money can buy. In our five-star Smarty review, expert Stuart Andrews praised the low-cost plans, top 5G performance, free EU roaming up to 12GB and solid customer service results of the mobile virtual network operator (MVNO), which runs on Three’s network.
A gigantic 92% of those we surveyed would recommend Smarty to a friend or family member and I’m more than happy to do the same. Its unlimited deal will set you back £20/mth on a rolling, 30-plan that you can cancel at any time. That’s not the cheapest offer around, but it’s still great value given Smarty’s quality.
Cons
The only gnat in the ointment was a fall in Smarty’s customer service satisfaction rate compared to the year before, while the company’s lack of eSIM support means that it’s not suitable for those with a slot-less phone.
Read our full Smarty review
2. EE: The best unlimited data SIM for speed
Price: £35/mth | View deal at EE
Pros
Picking up four stars out of five in our most recent EE review, the Kevin Bacon-toting mobile network impresses with its screamingly fast download speeds – still the speediest in the country after ten years – wide coverage, good customer service scores in our yearly Mobile Network Awards and a raft of extras.
EE’s best unlimited data SIM deal isn’t cheap at £35/mth on a rolling, one-month plan, but you’re paying a premium for what is essentially the Ferrari of mobile networks. According to the latest round of RootMetrics testing, its median 5G and 4G download speed was 61Mbits/sec, which is a country mile ahead of silver medallist Three’s 38Mbits/sec.
Cons
I can’t deny that EE is expensive and you can find more cost-effective offers lower down this list. You can lower the monthly price by signing up for a longer contract, but keep in mind that EE is one of the networks that has opted to increase prices mid-contract every spring by £1.50/mth.
Read our full EE review
3. Lebara: The best unlimited data SIM for calling abroad
Price: £25/mth | View deal at Lebara
Pros
Lebara is an MVNO that runs on Vodafone’s network and it’s a brilliant choice for calling friends or family abroad thanks to its bundling of international minutes. That’s why we gave it four out of five stars and a Recommended award in our full-length Lebara review.
This is my pick of the Lebara unlimited plans at the moment: if you sign up for the 30-day, rolling £25/mth option, you will get 100 minutes when calling 41 countries around the world, including India, the US, China, Australia, New Zealand, Thailand, Malaysia, Canada, Hong Kong and South Korea. What’s more, you’ll be able to roam for free in both the EU and India, up to a fair use limit of 30GB.
Cons
As with other networks on this list, the main downside was Lebara’s customer service scores in our annual Mobile Network Awards survey.
Read our full Lebara review
Why are other mobile networks not on the list?
There are a few household names missing from my list above but with good reason. In short, the reviews we gave them weren’t good enough to justify their inclusion. Below, I’ve rounded up a short explanation about why each of them was left out, complete with links to our full reviews.
1. Three: Lacklustre customer service
Three’s 5G performance and coverage results might have been good in our annual Mobile Network Awards survey, but it only received three stars out of five in our review due to its mediocre customer service feedback.
Read our full Three review
2. Vodafone: So-so performance
Vodafone also picked up a three-star rating in our review. While its bargain bundles certainly have the power to turn heads, it was let down by middling performance scores, below-average customer service and EU roaming charges.
Read our full Vodafone review
3. O2: Too expensive
O2 does do some things well, such as offering free roaming in the EU up to a fair use limit of 25GB, but it still received three stars out of five due to speeds that lag behind its rivals, low customer service scores and high prices.
Read our full O2 review
How do I find the best unlimited data SIM plans?
As Expert Reviews’ deals editor, there’s nothing I enjoy more than tracking down deals that will save you money without compromising on quality. A lot of thought, time and effort is involved in the process, but I’ve briefly summarised my methods below and you can find out more details in my article about how I source deals.
How good is the mobile network?
I bring together experts to produce in-depth reviews based on their years of mobile network-watching experience. That means every unlimited data SIM plan will be based on the latest in-depth review, along with the results of the Expert Reviews Mobile Network Awards customer survey. If a mobile network isn’t as good as the others or it hasn’t been reviewed yet, its plans won’t be recommended.
Is there something for everyone?
I realise that people have very different budgets, especially during a cost of living crisis. That means I’ll always make sure that there’s a worthwhile, budget-friendly plan in a roundup. That said, I won’t just recommend something because it’s cheap as you might end up having to pay more in the long run if the performance isn’t adequate.
Are there any hidden catches?
It can still be easy to stumble into a costly trap such as the new mid-contract price hikes, which see networks increasing prices by a set amount every year. This is usually set at the Consumer Price Index (CPI) rate of inflation plus an extra 3.9%, but Ofcom has now decided that companies need to outline the price increases in pounds and pence from January 2025.
Wherever possible, I’ll avoid recommending any deal that will become more expensive as time passes. However, if one does make the list, I’ll always be transparent in the mini-review and justify its inclusion.
How to choose the best unlimited data SIM for you
How much should you spend?
Prices for an unlimited SIM can vary wildly depending on the length of the contract and additional features you’re getting. As a rule of thumb, though, we would hesitate to pay more than £30/mth for an all-you-can-use 5G SIM on a two-year plan. Anything under £20/mth might seem like a bargain, but you could be sacrificing speed or coverage so be sure to check the small print.
Third-party sites such as Affordable Mobiles and Mobiles.co.uk can offer eye-catching savings on SIMs, though you will often have to claim back the money via cashback after a set period. If you don’t mind the bit of extra paperwork, go for it, but it’s always worth checking the network’s site beforehand to make sure you’re not missing out on goodies.
How long should the contract be?
You can normally pick between a one-month, 12-month or 24-month unlimited SIM contract. We would opt for a two-year plan because that’s how you can get the most browsing bang for your buck. The shorter contracts, meanwhile, will appeal to users who don’t want to be tied down for so long.
Does download speed matter?
Most mobile networks, with the notable exception of Vodafone, don’t specify a separate speed for their unlimited data SIM and include a flat rate across all of their plans. We’ve mentioned the most recent Opensignal 4G and 5G download speed results in the bite-size reviews above.
Is it worth getting a 5G-capable SIM?
5G has already been rolled out across dozens of towns in the UK, but huge swathes of the country still aren’t covered. Consequently, it’s worth checking if you’re able to get the fastest speeds before you make a buying decision – there’s no point paying for a service that you can’t access. That said, you will find that many of the best unlimited data SIMs are now 5G by default.
Will you be able to use the SIM abroad?
Most of the leading mobile networks will offer some kind of scheme for using your SIM on your travels. Some opt for a daily data cap, while others let you use your entire allowance as usual. If there’s a particularly holiday-friendly extra available, it will be mentioned in our reviews.
What extras should you look out for?
All unlimited data SIM plans come with endless minutes and texts as standard, but networks also try to stand out from the crowd by throwing in useful tools such as personal hotspots or treats like money off subscription services. We’ve mentioned any permanent extras in our reviews, but it’s worth perusing our list of the best time-limited SIM-only deals too.
