What is a SIM only deal?
A SIM only deal is a contract that includes minutes, texts and data for a monthly fee, but don't include a phone. SIM only deals are usually a lot cheaper than a standard mobile phone monthly contract that's bundled with a handset.
How does SIM only work?
It's precisely because SIM only deals don't include a phone that they're usually a lot cheaper than standard mobile phone monthly contracts.
A SIM card itself is a microchip around the size of a postage stamp holding all of a mobile phone's configuration information, for example the mobile phone number and call plan. Without a SIM card, a mobile phone will not work.
Once a SIM card has been activated it is permanently locked to the particular network, though not locked to a particular phone. That means you can easily change mobile phone handsets but keep your phone number, your friends’ phone numbers and any saved messages or photos.
Want a phone-and-tariff contract instead? Take a look at some of the best on the market at our dedicated comparison page.
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Why choose a SIM only deal?
If you're out of contract and happy with the phone you've got and don't want to upgrade to a newer model, it's smart to switch to a SIM only deal.
Otherwise, your network will continue to charge you the same monthly premium as when you were still paying for your handset. So going SIM only is a very good way to cut your outgoings and save some money.
More and more people are also opting to buy their phone outright and off-contract, then signing up for SIM only deal for data, minutes and texts. This can work out much cheaper than a standard phone contract.
But, of course, the catch is that you'll need hundreds of pounds to-hand to be able to buy a smartphone outright.
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I’ve found a good SIM only deal with my existing network. What happens now?
So you’ve chosen the SIM only deal you want and you’re certain you’ve fulfilled your contractual obligations. Good news.
All you need to do to now is phone up your network and tell them you’d like to switch to the SIM only deal you’ve selected.
You’ll then be transferred to your new SIM only deal 30 days after your current contract was due to end. It’s that simple.
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I want a SIM only deal with another network. What do I do?
The very first step is to check that you’re free to switch. The best way to do this to ring your network.
Once you’ve established that you are, pick a SIM only deal and network that suits you using the uSwitch comparison tables above and sign up for it. Your SIM card should arrive within two days.
In the meantime, ring or email your network to tell them you’d like to leave and ask them to unlock your phone.
You may find you're encouraged to stay by their customer retentions department. If you are it's important that you're firm with them and insist that you're determined to switch.
A charge may apply for unlocking your phone. But this will only be between £15-£20. Once the phone is unlocked you can insert your new SIM and you're all set.
If you want to keep your number, make sure you also ask your current network for a PAC code (Porting Authorisation Code) when you notify them you’d like to leave. We’ll look at how you use your PAC code more closely in the section below.
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How do I keep my number?
If you want to keep your number when you change networks, you'll need to ask for a PAC code from your current provider.
A PAC code is made up of three letters and six numbers and is provided free by your network.
To get your PAC code you can either phone or email your network or use a PAC code request form that you can fill on your network's website.
To begin the number transfter you need to ring or email the network you're joining and supply them with your PAC code. You must do this within 30 days of the PAC code being issued.
The transfer of the number is normally complete the next working day.
In the meantime, leave your old SIM in your phone. This means that apart from a very brief period when the transfer is actually underway, you’ll still be able to receive calls and texts on your phone.
To check if the transfer is complete, just insert your new SIM in your handset and see if your new number is registered on your new network. If you are, everything's gone according to plan.
Find out more about keeping your number when you switch with our one-stop guide.
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What do I do with my old SIM?
If you're worried that your SIM and the contacts, text messages and other personal information you've stored on it could fall into the wrong hands, you'll need to dispose of it carefully.
Just as you would with an old credit card, the safest thing to do is take the SIM and use scissors to cut it up.
While you're doing so, ensure you damage the gold foil so you make absolutely certain there's no way anyone can retrieve your personal information.
You're then free to throw the old SIM away.
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Will there be a credit check? What happens if I fail?
Whether you want to sign up for one-month rolling SIM only contact or 12-month SIM only contract with a new network, you'll have to pass credit check.
For pay monthly, rolling contracts, the credit check isn't as stringent as for 12 months. So if you've been rejected for a 12-month contract before, there's no reason to believe you won't be accepted.
But if you fail your credit check, that doesn't mean you can't get a good SIM only deal.
Pay as you go deals with some networks now offer monthly allowances that aren't much less generous than SIM only contracts.
The only major difference is that you'll have to remember to top up to ensure you've got credit.
Compare SIM only deals that don't require a credit check.
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Can I trust smaller, less well known networks? Is the service as good?
Although the likes of giffgaff and the people's operator aren't as instantly recognisable as high-street names such as Three, EE and Tesco Mobile, they're brands you can trust.
giffgaff, for instance, has won a slew of consumer awards, including Best Value for Money Pay Monthly from uSwitch.
In fact, many smaller networks offer market-leading call rates, so can work out cheaper.
You'll also find that there's no difference in call quality and mobile internet coverage with smaller providers.
That's because their service is based on larger providers' network infrastructure, which these smaller networks pay a fee to use.
Where you may find a difference compared with the larger networks is in customer support, however.
In order to keep prices low, some smaller networks don't operate a call centre and offer online support only.
If you choose smaller networks you also shouldn't expect enticing customer incentives, such as O2's Freebies or movie downloads with EE.
But you may decide that you don't want or need those and that a good service and cheap rates are your priority.
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MicroSIM? NanoSIM? How can I be sure I'm getting the right SIM for my phone?
Not all SIMs work in all phones. Micro SIMs are generally compatible with older phones, while newer models use Nano SIMs.
The only sure way to tell them apart is size.
A microSIM measures around 0.6” long by 0.5” wide.
A NanoSIM is a little bit smaller at 0.5” long by 0.3” wide.
The good news is that all UK networks now offer all-in-one Multi SIMs that fit your phone whatever kind of SIM you need. You're supplied with a large SIM card and then simply push out the size of SIM you need.
We haven't got the space to give you a definitive, exhaustive list of which handsets are compatible with which phones. But the listings below outline many of the most popular smartphones, as well as some of the older models, and the type of SIM you'll need.
Smartphones that are compatible with Nano SIM include:
- Apple iPhone 5/5s/5c
- Apple iPhone 6 and iPhone 6 Plus
- Apple iPhone 6s and iPhone 6s Plus
- Apple iPhone 7 and iPhone 7 Plus
- Apple iPhone 8 and iPhone 8 Plus
- Apple iPhone X
- Samsung Galaxy S6 and S6 Edge
- Samsung Galaxy S7 and S7 Edge
- Samsung Galaxy S8 and S8 Plus
- Samsung Galaxy Alpha
- Samsung Galaxy Note 5
- Sony Xperia Z5, Z5 Premium and Z5 Compact
- Sony Xperia Z3, Sony Xperia Z3+ and Z3 Compact
- HTC One M8, HTC One M9, HTC 10
- HTC U11 and HTC U Ultra
- HTC U Play
- HTC Desire 610 and Desire 816
- Nokia Lumia 1520, Lumia 650, Lumia 1320, Lumia 930
- Motorola Moto G5 and G5 Plus
Smartphones that are compatible with Micro SIM include:
- Apple iPhone 4/4S
- HTC One series phones prior to the M8
- Samsung Galaxy S3, S4 & S5
- Samsung Galaxy Note 2, 3 and 4
- Sony Xperia S & Z and Z2 series
- Motorola Moto G3 and G4
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Will I lose service if I switch to a SIM only deal with another network?
The process of moving network has been designed to keep the time you're without a service down to a minimum.
Even after you've given the network you're joining your PAC code (see above for a more detailed explanation of PAC codes), so you'll still be able to take calls and receive texts during this time.
When the transfer to your new network is actually happening, your service will be down for a very short period.
To test when the transfer has been done, simply insert your new SIM in the phone and restart it. If you've got a service, you're good to go.
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Which networks offer SIM-only deals?
SIM-only plans are available from all the major mobile phone networks and companies, including:
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Pay As You Go SIM only (PAYG) deals
The term 'pay as you go SIM only deals' is now commonly used to refer to one-month SIM only deals that operate on a rolling contract basis.
The principal appeal of these is flexibility. Because they don't tie you into a lengthy contract term, you can cancel with just 30 days' notice. And you're free to switch network or sign up for a better deal too.
Pay as you go SIM only deals tend to be pretty good value. At the time of writing, the cheapest start at not much more than £5 per month.
Think a pay as you go SIM only deal might be right for you? Take a look at what's on offer.
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Looking for a data only SIM deal for your iPad or tablet? Take a look at our data only SIM page or iPad SIM card page to find our best deals.
