Managing Editor for Broadband and Mobile

Last updated: 22 July 2025

4 mins read

Key points

If you switch to a Three SIM only deal, expect extensive mobile coverage and great rewards through this provider’s loyalty scheme
Three offers flexible SIM only tariffs to suit all budgets, so you’re never overpaying for what you use
Activating your new Three SIM is easy, whether you’re an existing customer or have just joined the network; simply follow the instructions and you’ll be good to go
Whatever your travel plans, Three SIM only can support these as well, with roaming available across more than 70 worldwide destinations

What is Three SIM only?

As one of the biggest mobile operators in the UK, Three has its own network and, at the time of writing[1], offers 99% 4G coverage.

What’s more, Three has rolled out 5G services to approximately 400 towns and cities across the UK, with plans to keep growing this infrastructure so customers can stay better connected.

The Three+ loyalty app gives you access to some amazing perks, including various discounts and exclusive pre-sale tickets for events, like music gigs.

Why choose Three SIM only?

Some reasons for choosing a Three SIM only deal include:

Affordability

Three offers a trio of SIM only plans:

Lite
Value
Complete

While ‘Lite’ tariffs tend to work out the most economical due to their limited extras, it might be better for you to consider a ‘Complete’ deal, which offers more perks.

However, this will depend on how often you plan on using them.

5G as standard

Even with its most basic tariff, Three offers 5G to customers with compatible devices.

This means you can get the fastest degree of connectivity available right now.

Flexible data

You can choose from a variety of data limits on Three SIM only deals.

Whether you want to go fully unlimited for maximum convenience or only need a 1GB allowance for casual roaming, Three can provide you with the data you need for your everyday activities.

What Three SIM only deals are there?

Offering a wide range of pay monthly and Pay As You Go SIMs, Three can not only connect up your phone but also your tablet and/or mobile broadband with these types of tariffs.

All Three SIM only deals include unlimited minutes and texts, plus 5G speeds as standard on any compatible mobile device.

Customers can also get access to streaming services such as Paramount Plus, exclusive Three+ rewards, and global roaming across over 70 worldwide destinations.

How much is Three SIM only?

Three offers a wide range of SIM only plants to suit all budgets, although its Lite tariffs tend to be the most cost-effective.

At the time of writing[2], you can also get three months free on your new SIM purchase.

Other benefits for Three customers include:

Three+ rewards scheme
Unlimited picture messages
5G at no extra charge (on compatible devices)
Access to Paramount Plus (with selected tariffs)

How to choose Three SIM only deals

Things to keep in mind when comparing Three SIM only deals include:

Data habits

Whichever Three SIM only plan you choose, make sure there’s enough data on it to support your day-to-day mobile usage.

For example, if you travel a lot for your job and need your mobile to make important work calls while on the go, you’ll probably need a more generous data allowance than a customer who works almost exclusively from home.

Budget

It may be tempting to opt for a Complete plan with Three, but consider if the add-ons it gives you are worth the extra money.

If you think you’d be better off with a Lite tariff, covering your everyday mobile essentials, then choose this type of plan instead.

Flexibility

Three SIM only deals come with a decent degree of flexibility.

Whether you want to commit to a 24-month contract or are looking for something short-term at around 30 days, Three SIMs are as flexible as you want them to be.

How long is a Three SIM only contract?

Choose a Three SIM only contract for:

24 months
12 months
1 month

Whichever SIM you pick depends on:

How important flexibility is to you
Whether you want a long or short-term deal

Activating your Three SIM

To activate your Three SIM, follow these steps:

Turn your mobile phone off and put the new SIM into it
Switch your device back on
1. Three should text you to let you know they’ve begun activating your SIM. Allow up to 30 minutes, at least; it could even take longer when periods are busy. DO NOT switch off your phone during this time
Once setup is complete, Three should send you a second text message telling you to turn your phone off and on again
When you restart your phone, the new SIM should be activated; if successful, Three will confirm this with a third and final text

Any problems activating your new Three SIM should be referred directly to Three customer support.

Can you keep your current number with a Three SIM only deal?

If you’re an existing Three customer switching to a SIM only deal, you don’t need to do anything in order to keep your current number.

For customers who are moving across to Three from a different network, you’ll need a porting authorization code (PAC), which you can request by calling your old provider.

Alternatively, you can request your PAC by texting ‘PAC’ to 65075.

Once you have your PAC, call Three to provide this information and they should be able to switch you over to their network within one working day.

Are Three SIM only deals an option with poor credit?

Three offers a basic Pay As You Go SIM only deal that doesn’t require a credit check.

This tariff works on a traditional PAYG model, whereby you top up using credit for calls, texts and data.

Three should notify you via text message if it looks like you’re about to run out of credit and need to top up.

Can you use your Three SIM only plan abroad?

If you’re travelling outside the UK, you can still use your Three SIM only plan.

Depending on your destination, you’ll probably have to pay extra for the privilege, as Three is one of the many network providers that reintroduced EU roaming charges after Brexit.

However, on certain plans, Three does let you ‘roam like you’re at home’ for up to a specified number of days.

That, and its inclusive ‘roaming passes’ are valid around the world, with the most generous offering coverage in over 70 global destinations.

What happens when you reach the end of your Three SIM only contract?

Once near the end of your Three SIM only contract, they'll contact you to let you know and make you aware of any new deals they have available.

You can always continue on the same SIM only tariff; however, it might be a good idea to look elsewhere and see if there's a better tariff for you.

Compare mobile phone deals across a variety of networks to make sure you're on the right plan.

Compare Three SIM only deals with other networks

Take a look at how Three SIM only deals look alongside those offered by other UK mobile providers, including:

[1] Information correct as of January 2024.

[2] Ibid.