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The best SIM only deals: prices and plans compared

SIM only deals are an option growing in popularity recently, offering an alternative option to long inflexible phone contracts. And whether you've bought a SIM-free phone or your contract has ended and you're looking to hold onto your device, finding a SIM plan is the next step.

While a few names are likely to come to mind first including EE, Vodafone, Three and O2, there are plenty of networks available to get SIM only deals from, all offering unique selling points and features.

The likes of Smarty and GiffGaff are offering cheap and flexible 1-month rolling plans, Virgin and iD Mobile can roll your data over each month and Voxi can land you unlimited use of social media and streaming apps.

In other words, when it comes to SIM only deals there is a lot of choice out there right now. If you already know everything you need to know about SIM plans and just want to find the best price, use our price comparison chart below to see the cheapest options.

Or if you're still unsure whether a SIM plan is the right option for you, we've answered some key questions further down this page.

The best SIM plan right now:

Three | SIM only | 12 month contract | Unlimited data, calls and texts | £16 per month
This SIM plan from Three has dominated the market since it appeared, offering an excellent level of value. For the price of just £16 a month, you're getting unlimited data, calls and texts. Despite that unlimited cap, this is still cheaper than most other big data SIM plans around.

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What is a SIM only deal?

A SIM only deal is a contract that supplies you with a SIM card with a select balance of minutes, texts and calls each month for your phone. They vary in cost, data caps and contract lengths.

The three best SIM only deals on the market:

Three | SIM only | 12 month contract | Unlimited data, calls and texts | £16/month from Three
Three is the ruling SIM right now. It offers unlimited data, calls and texts all for just £16 a month. This SIM is also 5G enabled so you can use it in any 4G or 5G phone. While there are cheaper options than this, Three has the overall best value.
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EE | SIM only | 12 month contract | 120GB data | Unlimited calls and texts | £20/month from EE
For a lot of people, the EE network will be the obvious choice thanks to its super fast speeds. Right now, this is the best EE plan available, offering 120GB of data for just £20 a month. On top of that, EE offers a lot of free subscriptions to MTV, BT Sport and more if you text certain numbers once you're signed up.
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Smarty | SIM only | 1 month contract | 30GB data | Unlimited calls and texts | £10/month from Smarty
Smarty has an excellent offer for those on more of a budget. It supplies 30GB of data for just £10 a month. That's the best option for a price as low as this and on top of the cost and data perks, Smarty operates on 1-month rolling contracts so you can leave at any time.
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Why get a SIM plan?

While a regular phone contract is often the better known option for those needing a new phone, a SIM plan can actually be the better choice for a lot of people. Whether you pair it with a new SIM-free phone or one that's come from a finished contract, a SIM is far cheaper.

As we said above, there are usually two situations where a SIM only deal comes into play. The first is if you've had a phone contract and it has come to an end, if you're happy with the device you had you can extend its life by buying a new SIM.

The other option is perfect for those with a bit more cash to spend upfront. Whether it's a flagship phone or something budget, buying a phone SIM-free and pairing it with a new SIM only deal is the overall cheapest way to get a new device.

What factors should be considered for a new SIM?

There is just a few factors that are worth considering when purchasing a new SIM plan, these are:

- Contract length:
SIM only deals tend to come in one of three lengths: 1-month rolling, 12-month or 24 months. Due to their flexibility, rolling contracts are the best option but these are limited to a few lesser-known brands.

12 and 24-month contracts are more common and tend to offer an overall better price point. These are where you'll find networks like EE, Three, Vodafone and O2.

- Data, minutes and calls cap:
This is likely the main factor you'll be looking at. While most SIMs will secure you an unlimited amount of calls and texts, data caps can fluctuate hugely between SIMs and networks.

These can range from the very affordable but limited 500MB-2GB and all the way up to 100GB+ plans and unlimited data offers. Obviously, prices tend to increase based on how much data you add.

- Price:
Over time, SIM plans have become cheaper and these days most of them are pretty affordable. However, if you know you won't need a huge amount of data you can keep your prices below £10 a month quite easily.

Big data plans, ranging from 50GB upwards through to unlimited, can see you spending anywhere from around £15 through to £30+. Whatever your price point is, it is worth considering a few networks to see which can secure you the most data.

- Network:
There are plenty of networks to choose from for your SIM plan and many of them have certain benefits that make them stand out. Three offers big data plans at low costs, iD Mobile, Giffgaff and Smarty Mobile run on 1-month contracts and Voxi offers unlimited usage of social media apps or streaming services.

For a number of years, EE has been the most popular network due to its position as the UK's fastest network on both 4G and 5G. It also offers a host of free subscriptions and data sharing to make it an advantageous network. Most network websites will let you check the strength of its signal in your area which is something we'd recommend checking before you buy.

- 4G or 5G?
It's becoming more and more common for phones to come with 5G features these days and while that is great, if you've got a 5G phone you'll need a 5G SIM to go with it.

Some providers like Three and Vodafone automatically offer both 4G and 5G across all of their plans. However, others will require you to spend more to get 5G like EE or Voxi.

A number of networks also don't have 5G yet and are unlikely to until a decent way through 2021. With this in mind, if you've bought a 5G phone, consider this factor with your new SIM.

SIM only deals: unlocking phones and PAC codes

Changing your number to a new SIM:

If you're changing to a new SIM plan from an old one, you'll need to transfer your details across. While this used to be a pretty complicated process, it has become a lot simpler recently.

All you need to do is track down a PAC code. That sounds more complicated than it is as a new 'text to switch' concept was brought in recently. All you have to do is text the provider you were with and they'll reply with a code (that lasts for 30 days).

This code can then be given to your new network and voila! You're transferred. You can find out more about each network's PAC text to switch system on their websites as each network uses a different number and system.

Unlocking phones and using SIMs with them:
If you're buying a brand new SIM-free phone then you can skip right on from this section, same for anyone who's staying on the same network but changing plans.

However, if you're transferring to a new network, you could be in the position where you have a phone locked to a network. Don't fret though, this can be easily solved.

Three automatically unlocks a phone that was once on its network and O2 will unlock it for free. Vodafone also does it for free but it can take some time to process the request. 

EE is a little bit different and can charge you £8.99 for the privilege of getting your phone unlocked. Other networks like Virgin, Voxi and GiffGaff all operate differently so consult their websites to find out exact details.

SIM only deals: each network's benefits

EE:
EE is the most popular phone network in the UK, mainly down to its speeds. For a number of years now, EE has been the UK's fastest 4G network and now, it is also the fastest 5G network. On top of its speeds, it offers data swaps between family plans, free subscriptions and more. However, it also tends to be one of the pricier networks.

Three:
For pure value, Three tends to be the best option when you get into the bigger data packages. It offers 4G and 5G connections on all of its plans and frequently has the UK's cheapest unlimited data SIM plan. However, past its affordability, 5G upgrades and big data plans, there isn't much more to see.

O2:
O2 is one of the four main networks including EE, Three and Vodafone as the others. It offers an overall impressive performance, giving good coverage, affordable prices and good data plans. It also includes its O2 Priority scheme with free gig tickets, coffees and other similar benefits. O2 has also started including Disney Plus with a number of its SIM plans.

Vodafone:
Vodafone is a network that is a lot like O2 in many ways. Like O2, it is has good coverage, affordable pricing and pretty strong data plans. Also like Vodafone, it has one of the better reward schemes - VeryMe. However, if you decide to go for unlimited data with Vodafone, be wary of which plan you choose, some can cap your speeds, offering a lower price in exchange.

Virgin:
As a network piggybacking off EE, Virgin's biggest benefits are its speeds. It has all of the same reach, coverage and speeds as EE but often for a lower price point. However, other than this, Virgin isn't a network with many exciting features.

Smarty:
Smarty has three major benefits under its belt. It operates on 1-month rolling contracts so you can leave at any time, it's incredibly affordable and it allows you to tether no matter which plan you have (perfect for those on the unlimited option).

Voxi:
At one time, you had to be under 30 to sign up with Voxi...for some reason. But recently they've opened their doors to everyone - good news considering it has some pretty strong offers. Not only does it use 1-month rolling contracts but it also offers unlimited usage of social media on all of its plans. Certain other plans offer 5G or unlimited use of streaming platforms Like Netflix and YouTube.

Giffgaff:
GiffGaff is possibly the best known of the 1-month rolling SIM providers and although it boasts "the mobile network run by you", it actually uses the O2 networks to run. It now also offers 5G on certain plans and is a good option for those needing an affordable and flexible SIM plan.

Thinking of picking up a new phone? Check out our list of the best gaming phones. And we'd thoroughly recommend checking out our favourite phone of 2020 with our Samsung Galaxy Note 20 Ultra review. If you're after a much cheaper alternative though, our iPhone SE 2020 review might sway you.

Alex is an editor of broadband, phones and SIMs at Future with a primary focus of bringing you the best deals and knowledge across these areas. Whether you need a new SIM plan or a superfast broadband plan, he's on the case