If you own almost any kind of mobile phone, you’ll need a SIM card to access its full range of features.
This allows you to make calls, send texts and use the internet while out and about – essentially, anywhere you can’t connect to Wi-Fi.
It’s fundamental for a basic phone, but also necessary for nearly every smartphone owner.
However, even after you’ve secured the phone and potentially got a great SIM-only deal, there’s one more crucial step: activation. This will register it to your specific handset and allow you to start using the minutes, texts and data you’ve paid for.
But the process varies slightly depending on which network you’re with. In this article, we’ll run through what you need to with all the most popular providers in the UK and US.
What types of SIM are there?
Before going through the activation process, it’s worth being aware of the different types of SIM out there.
Most are still physical cards which must be manually inserted into the phone, but they come in three different sizes.
The smallest of these, a nano SIM, is by far the most popular these days. It’s what you’ll find in almost every smartphone.
But there are plenty of devices still using micro SIM, the next size up. These are still common in many basic feature phones.
The full-size SIM has been phased out almost completely. You’ll only find it on a handful of phones, most of which are very old.
The good news is that when you buy a SIM card, you’ll usually get all three types. And it’s easy to simply pop out the version you need.
To put it into the phone, you usually need a small ejector tool to access the SIM tray. These are normally included in the box with a new phone, or very cheap to buy. But if you need one right now, try a paper clip, safety pin or earring, but take extra care not to damage the phone.
It’s less important these days, but you can actually use a nano SIM in a phone which takes a micro SIM using an adaptor (such as the one often included when you buy the SIM). It doesn’t work the other way, though – a micro SIM is too large to fit into a nano SIM slot.
And make sure you never insert an adaptor without the SIM card in the middle. It may get caught on the metal prongs inside the slot, and could do serious damage to your phone if you have to remove it with force.
We’re focusing on physical SIM cards here, but there is another type these days: eSIM. These are digital versions of SIM cards that work in much the same way. The only real difference is that instead of physically moving a card between devices, you’ll need to head into settings to deactivate it on one phone and activate it on another.
But there are a few other things to be aware of, as is explained in our guide to eSIM.
How to activate a SIM card
To activate any new SIM on any network, you’ll need an unlocked phone. This is likely to be the case if you bought your phone outright, but there are exceptions to this, so it’s worth checking.
But if you’ve bought the phone on contract, it’ll probably be locked to that specific network – at least until the contract is up and you get to keep the phone. If that’s the case, it won’t be possible to activate a new SIM.
The only other step not mentioned below is if you’re using a pay-as-you-go (PAYG) SIM instead. In that case, you’ll need to top it up before it’s activated.
Here’s how to activate a SIM you’ve bought on any of the main networks in the UK and US. After you complete the steps below, activation will take up to 24 hours, but it’s usually much less.
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EE and operators that use its network
For most people, activating an EE SIM is as simple as inserting it into your phone, turning it on and then filling out the form on the EE website. This includes a one-time PIN sent to your old number, so make sure it can still receive texts.
Once active, you should see a signal available and an indication that you’re connected to the EE network. But if you’re using an iPhone, it may also be necessary to refresh iMessage:
- Head to Settings > Messages. Turn iMessage off, wait 10 seconds and turn it back on again
- Head to Settings > Phone and make sure ‘My Number’ matches your new one. Tap it to edit if this isn’t the case
For the most popular providers that use EE’s network, see information on the BT Mobile, Lycamobile and Utility Warehouse websites.
Vodafone and operators that use its network
On Vodafone, insert the SIM, turn on the device and wait for signal to appear.
However, if you’re moving from another network, you might need a Network Unlock Code (NUC) from your previous provider. How to do this depends on which network you’re coming from – if leaving Vodafone, you just fill in the online form.
For the most popular providers that use Vodafone’s network, see information on the Voxi, Asda Mobile and Lebara websites.
O2 and operators that use its network
O2 pay monthly SIM-cards are pre-activated, so you’ll just need to turn off the phone, insert the SIM, turn it on again and wait.
For the most popular providers that use O2’s network, see information on the Giffgaff, Sky Mobile and Tesco Mobile websites.
Three and operators that use its network
On Three, insert the SIM and switch it on.
You should receive a text to the new number saying the activation process has begun. Three says it usually only takes 30 minutes, but can be longer, and you’ll need to keep your phone on throughout.
You’ll then be texted asking you to turn your phone off and on again. A third text will then be sent to confirm that activation is complete.
For the most popular providers that use Three’s network, see information on the iD Mobile, Smarty and Honest Mobile websites.
Want to know more about how the UK providers are different from each other? See our dedicated guide to the best UK phone networks.
T-Mobile and operators that use its network
On T-Mobile, you’ll also have to insert the SIM while the phone’s switched off, then turn it on.
Follow any setup prompts that appear on your screen, which will include logging in to your T-Mobile account. You should already have one, but you can register for a new one if necessary.
Once that’s done, call 1-800-T-MOBILE from your new phone to complete activation.
For the most popular providers that use T-Mobile’s network, see information on the Mint Mobile, Boost Mobile and Ultra Mobile websites.
AT&T and operators that use its network
The same first few steps apply on AT&T. Turn off the phone, insert the SIM and then turn it on.
Then, fill out the activation form on the AT&T website with your new number and ZIP code and follow the steps on screen.
For the most popular providers that use AT&T’s network, see information on the Cricket, Boost Mobile and PureTalk websites.
Verizon and operators that use its network
On Verizon, you’ll also have to turn off the device, insert the SIM and turn it back on.
Then, head to the Activate or Switch Device page on the Verizon website and follow the steps to complete activation. This will require you to log in to your My Verizon account or create a new one.
For the most popular providers that use Verizon’s network, see information on the Visible, Xfinity Mobile and Tello websites.