Choose a UK SIM

The short version

For your first UK SIM, you want something that doesn't lock you in. Start on a monthly rolling plan for a month or two, work out how much data you actually use, and only then decide whether to sign a long contract. Do it the other way round and you'll probably pick the wrong plan and be stuck with it.

Why signing a long contract on day one is a bad idea

• You don't know how much you'll use yet. Some people arrive, find Wi-Fi everywhere on campus and at home, and use less than 5GB a month; others are out all day running a hotspot. Until you've done a month, any plan you pick is a guess.
• Where you live, your uni, even your city might change. The contract follows you; good signal doesn't.
• Leaving early means paying an exit fee, whereas the most a rolling plan can cost you is this month's bill.

What the plans look like now (giffgaff as the example, website checked 2026-09-05)

It splits its plans into three types, and for your first UK SIM, it's the "monthly rolling" column you want:

At the time, the rolling price was 20GB for £10 a month (below that, 5GB for £8 and 2GB for £6; above it, 50GB for £15). These numbers move every few months, so don't copy them – the date checked is above, so look again before you order.

To be fair: the 18-month contract page says "no credit check" and "no price rises during your contract", which honestly isn't a bad deal. So the point isn't "contracts are all rip-offs" – it's that you're not yet in a position to know which plan suits you, so don't bet 18 months on it yet.

Four steps

1. First, check your phone isn't network-locked. A phone bought on contract back home may only work on that network; if a new SIM gives you no signal, check this first.
2. Pick a monthly rolling plan and start in the middle. Around 20GB is plenty for most people.
3. If you want an eSIM, set it up the same day; if you want a physical SIM, have it posted to your halls. Sort it before you land and you'll have a number when you step off the plane.
4. After a full month, check your bill for what you actually used, then decide whether to go up, go down, or start comparing long contracts.

Common traps

• Buying a "tourist SIM" at the airport. It's the most expensive option, and it usually runs out after a few days.
• Being won over by "the contract's a pound or two cheaper". A pound or two a month buys you a year and a half of being stuck.
• Treating an offer price as the normal price. Time-limited deals go back to full price when they end, and you only notice in the month it renews.
• Forgetting it renews automatically. If you're not using a rolling plan, cancel it – don't let it keep charging you.

Why this has to be sorted before you fly

No signal for your first few hours amplifies every other problem: you can't book a cab, open a map, get verification codes, reach your landlord, and your family can't reach you either.

And it takes ten minutes to sort before you leave. So there's just one rule here:

Don't count on "I'll figure out data when I get there".

About "I'll just buy a SIM at the airport"

Don't bank on it. You might land at dawn or late at night, the shop might be shut, there might be a queue, you might have to sort it out in English, or there might only be pricey tourist SIMs.

It's fine as a backup, but it isn't a plan.

Three options, safest first

Option 1 (safest): install an eSIM that works on arrival before you go

An eSIM is a SIM with no card: you scan a QR code or install a profile on your phone and it's live, no waiting for post. Install it before you leave, turn your phone on when you land and it connects – the least hassle of the lot.

You'll need: a phone that supports eSIM (most recent models do; check in your settings before you go), and one that isn't locked to a network.

Option 2 (fallback): turn on roaming with your home network

Before you leave, turn on international roaming in your network's app or with customer service, and it'll work when you land.

Every network's prices and rules differ and change often, so this guide gives no figures. Before you go, ask customer service or check the app, get answers to these three, and screenshot them:

1. Is international roaming switched on for my number? (if not, turn it on now – it usually works straight away) 2. How is data charged in the UK? Is there a daily cap, and how much is it? 3. What happens once I go over the cap? Do I need a separate data add-on?

Don't go by anyone else's figures (including the "I think it's capped at thirty a day" kind) - they differ by network and plan, and change every year. Ask about your own SIM and screenshot the answer.

Roaming is a stopgap, not a long-term fix: it gets expensive, and lots of things here want a UK number (registering with a GP, the bank, food delivery apps and parcel texts may all ask for one).

Option 3 (you didn't get round to anything): use free Wi-Fi when you land

Airport terminals have free Wi-Fi (you'll usually need to enter an email address or phone number). Use it to:

1. Let your family know you've landed safely;
2. Book a cab / look up your route (screenshot the route – you may lose signal once you leave the airport);
3. Get on your landlord's or halls' Wi-Fi when you arrive, then sort a SIM without the rush.

It'll get you out of a hole, but it makes arrival day stressful – try not to end up here.

Once you're here: get a UK SIM

When to get it

In your first few days. Signing up at uni, opening a bank account and registering with a GP often ask for a UK mobile number.

Which kind

Don't sign a long contract straight away. Start on a rolling monthly plan for a month or two, see how much you actually use, then decide whether to commit – the reasons and plan types are in "Don't sign a long contract for your first SIM".

giffgaff as an example (an example we checked, not a recommendation)

• Physical SIMs are posted free, the card itself costs nothing, and you only pick a plan and pay when you activate it; it's a three-in-one card (standard/micro/nano), so pop out the size your phone takes;
• On rolling monthly, 20GB is £10 a month (checked 5 September 2026), with smaller plans below that;
• It does eSIM (the help centre has a page on it). But we haven't checked whether you can activate it while you're still abroad and use it the moment you land - if you're going this way, check on their website before you leave.

Compare similar plans from other networks yourself. We're not picking a network for you.

Three small things nobody warns you about

1. Don't cancel your home SIM. Your apps, bank and payment services back home send verification codes to it. Before you leave, call your network and switch to the cheapest plan that keeps the number alive, then keep it in your second SIM slot or an old phone for texts only, no data.
2. Settle on your long-term UK number before you register with uni, the bank or a GP. They all keep your number, and changing it means updating every one; if you do switch network, take your number with you (see "Switch network, keep your number"), don't get a new one.
3. If your phone was bought abroad, check two things before you go: it isn't locked, and it supports UK 4G/5G bands (search your model plus "UK bands"). When people say a phone from abroad "gets bad signal", it's usually missing bands, not the network's fault.

Two tips from the airport (unchecked, from students who've done it)

The most obvious SIM counter in arrivals is usually the priciest; walk a bit further to the Tube level or a convenience shop and the same SIM is often much cheaper, and staff will help you activate it. That's experience, not a rule – prices and shops change, so don't make it your plan. Same message: sort your data before you fly.

Three ways to get the order wrong

1. Waiting until you land to order a physical SIM – post takes a few days, exactly when you need data most;
2. Getting the SIM, then finding your phone is locked – a phone bought on contract back home may only work on that network, so check it's unlocked before you go;
3. The SIM's sorted, but your payment card doesn't work – signing up for a SIM and getting around both need a card that pays, see "Sort out a card that works before you land". TfL also warns: a non-UK card in a phone wallet might not work, or could be charged overseas transaction fees.

On arrival day, you're done when

Your phone has data + you can receive verification codes. Both, or it doesn't count - plenty of people get stuck with "data, but no codes from home", and banks and uni registration often need those codes.

Why this is worth knowing

In your first week you gave your number to your uni, your bank, your GP, takeaway apps and couriers. A month later you spot a much cheaper deal elsewhere - and a new number means updating all of them, so loads of people just stick with the expensive one.

But in the UK you can switch network without changing your number. The regulator, Ofcom, sets the rules, and they have teeth.

Step by step (Ofcom's rules, checked 5 September 2026)

Step 1 · Get your new SIM and activate it

Get the new network's SIM and activate it first (for now it'll have a temporary number). Don't cancel your old SIM yet.

Step 2 · Ask your old network for a PAC: send one text

From your old SIM, text the single word PAC to 65075.

Ofcom's deadlines:

• Ask by phone and they must give it to you there and then, or text it within two hours if they can't;
• Ask by text or online and they must send it within two working days.

It comes with details such as any early termination charges. On a rolling plan there usually aren't any, but on a contract there might be, so take a look.

Step 3 · Give the PAC to your new network

Find "keep my number" or "switch" in your new network's app or website, and enter your old number and the PAC. A PAC lasts 30 days. If it runs out, just ask for another.

Step 4 · Wait one working day

Under Ofcom's rules, once you've handed over the PAC, your number should normally move within one working day. You'll lose signal briefly while it happens, so some people do it on a day they're staying in.

Not moved after one working day? You're entitled to compensation from your network (Ofcom's wording: reasonable compensation). That's a rule, not a favour.

Step 5 · Check it's done

Your new SIM shows your old number, and the old SIM stops working on its own. That's it, you're done.

Don't want to keep your number?

Text STAC (not PAC) to 75075, then give the STAC to your new network.

Two rules that protect you

• No paying twice: Ofcom bans your old network from charging for a notice period after you've moved – as long as you used a PAC or STAC, so the two networks can match up the dates;
• You can get your number back after cancelling: even if you've already cancelled your old service, you can contact your new network within one month and move your old number across for free.

Common mistakes

• Cancelling your old SIM before getting the PAC – then you can't send the text, and you're stuck with the "within one month" route, which is more hassle;
• Doing it on a Friday evening – only working days count, so you could be waiting until next week;
• Sitting on your PAC – it expires after 30 days.

Contains Ofcom copyright material: "Switching – mobile".