Not sure whether to join O2 or Three?
Today, we’ve compared these two mobile networks to see which is best, by testing a pay as you go SIM from both of them.
We’ve assessed Three and O2 based on their speeds and coverage, value for money, customer service, and more, to help you decide which is right for you.
Before we begin, if you’re searching for a new mobile plan, on any network, use our comparison site to find the cheapest pay monthly phone plans or SIM-only deals on the market right now.
Contents
- Overview
- Coverage and speeds
- Roaming allowances
- Value for money
- Customer service
- Verdict: should you join Three or O2?
Overview
O2 and Three are two of the big four mobile networks in the UK, alongside EE and Vodafone.
They both offer a range of different pay monthly phone and SIM-only deals, and operate their own network infrastructure. Meaning, if you buy from Three or O2 directly, there will be no throttling or deprioritisation of your traffic – you’ll have full access to the network.
Both providers offer unlimited calls and texts on all of their plans as standard, and allow you to get an eSIM instead of a physical SIM card, if you’d prefer – though O2 doesn’t support eSIMs on their pay as you go plans at the moment.
The benefit of O2’s pay as you go plans compared to Three is, they support data rollover, allowing you to use your leftover data during the next month, up to a certain limit. Plus, some of their month-to-month SIMs come with included international minutes, which is nice.
Of the big four mobile networks, Three and O2’s contracts are probably the most basic, which can be a good thing, because this means they don’t cost as much – though we’ll discuss these providers’ value for money a bit later in the article.
O2’s plans tend to come with more extras, at least on their pay monthly contracts. For example, you can sometimes get the choice of an entertainment add-on, such as Amazon Prime or Disney+, with a phone contract.
Three does a similar thing, offering Paramount+, but only on their more expensive plans. You also get access to their Three+ rewards program, even on a pay as you go SIM – giving you discounts on takeaway food, cafes, and entertainment.
It’s also worth mentioning, O2 gives you a speed boost on your Virgin Media Broadband plan, if you have one, when you sign up for a pay monthly contract.
Coverage and speeds
Three beats O2 when it comes to 5G speeds and coverage, but O2 has the upper hand when it comes to 4G signal.
Neither of these networks has speed caps on their plans, unlike Vodafone and EE, but Three is generally faster if your phone supports 5G.
According to Ookla, Three has a median 5G download speed of 236 Mbps, compared to just 74 Mbps with O2 – meaning Three is three times as fast.
Despite this though, O2’s 5G coverage is good, and we still saw strong download speeds on their network from our testing. They’re actually faster than Three on our street, especially when it comes to upload speeds.
Also, O2 performs quite well when it comes to 4G, again beating Three in our area.
We think that these 4G tests are a bit more indicative of national performance compared to the 5G ones – though Three’s upload speeds are normally a bit better than this.
O2 has very strong LTE – potentially second-best in the UK, behind EE.
Their speeds and coverage are very good on 4G, making O2 quite a good choice if you often struggle for coverage on other networks.
When it came to call quality, including using WiFi calling and VoLTE, we didn’t experience much difference between the two providers.
There were parts of the countryside where we could make stable calls with O2 and not with Three, but only in very remote areas.
Roaming allowances
O2 is a better choice than Three when it comes to roaming.
Three’s international usage policies are a bit complicated, but in short, on pay monthly plans, you normally need to pay either £2 or £5 per day to use up to 12GB of your allowance per month overseas.
This is, unless you have one of their more expensive tiers of pay monthly plans, with inclusive roaming included.
You can also buy longer-term roaming data allowances, if going on a longer trip.
But with O2, they include free roaming in 48 European destinations, up to 25GB of monthly data, on all of their plans.
And beyond Europe, it’s relatively easy to buy an O2 Travel Bolt On to unlock your allowance, at least as a pay monthly customer. These bolt-ons are actually included as standard on some of their more premium tariffs.
So not only is O2 roaming more simple, it covers more countries, and generally doesn’t cost money, at least in the EU.
By comparison, Three’s roaming allowances are quite complex, and can get expensive on longer trips, if you don’t have a pay monthly plan with free roaming included.
Though it is worth mentioning, Three’s roaming allowances are a lot better for pay as you go customers. On their month-to-month plans, there are generally no fees to unlock your allowances, except in certain less common destinations outside the EU.
Value for money
Three is generally a lot better value for money than O2.
If you compare their SIM deals with similar amounts of data, whether pay monthly or pay as you go, Three tends to be quite a lot cheaper.
This applies to both SIM-only contracts and pay monthly phones.
Below, we’ve displayed the cheapest deal from Three or O2 on the newest Apple, Samsung, and Google phones, based on the average monthly cost over the life of the contract. Most of the time, you’ll see Three deals displayed here.
This isn’t necessarily to say Three always offers the best value for money.
If you want to prioritise 4G coverage over 5G speeds, or want better inclusive roaming allowances, it still might be worth paying more to join the O2 network.
What we recommend doing is, use our smartphone or SIM-only deals pages to compare different tariffs on Three and O2, based on how much data you need, and what phone you want (if any).
Then, once you find some deals you like, look at more details about each of them on the providers’ websites, such as the extras included, to see which makes the most sense for you to buy.
Customer service
Each quarter, Ofcom releases data about the number of complaints they receive from customers of each major British mobile network.
Currently, O2 receives four complaints per hundred thousand customers, while Three receives three.
While these numbers are quite close, O2 is the worse of the two providers. And their complaints figure is actually the highest of any major network. EE and Vodafone only receive two complaints per 100k subscribers.
In our experience, we also think Three’s customer support is a bit better than O2’s.
They’re quick to answer the phone, and their team is quite knowledgeable about network and billing-related issues, even though they’re not UK-based.
Three also has a live chat, which can take a little while to connect you to someone, but is a good way to get support, in our experience.
With O2, some of their support team is UK-based, though occasionally you’ll get connected to someone in South Africa instead.
We just generally found that O2 customer support took a bit longer to get in contact with, especially over the phone.
We also think that Three’s team is a bit more helpful, when we raised similar sorts of billing and connectivity issues with both providers.
Verdict: should you join Three or O2?
Whether Three or O2 is the right choice depends a bit on what you’re looking for.
If you want the fastest possible 5G, or the cheapest prices, Three is your best choice.
But if you’re concerned about your overall signal, especially on 4G in remote areas, O2 might be a better pick.
O2 also beats Three when it comes to roaming, and we think the range of extras they include can be better – especially the Virgin Media speed boost, if you use Virgin Media Broadband.
On the other hand, Three’s customer service is a bit better than O2’s in our experience at the moment.
If you have any questions about the differences between these mobile networks, leave us a comment below, and we’ll get back to you as soon as we can.
About the author
Tom is the founder of Green Smartphones. You’ll find him writing about phones on the Green Smartphones blog, or talking about SIM deals and mobile networks on our YouTube channel. He’s the Android expert on the team – currently using a Google Pixel 9, recently upgrading from a very long-suffering Note 20 Ultra. When he’s not working on Green Smartphones, you’ll find him playing football or hiking.