The best of the major phone networks

As noted above, it’s existing Virgin Media customers who get the best value from O2, with bundle deals that are much cheaper than the SIM-only deals you’ll see in our table below. If you’re already a Virgin Media customer, log in to the Virgin Media website, select upgrades in your contract menu and check the ‘Volt benefits’ on offer.

If you’re buying SIM-only and you’re not typically a heavy data user, O2 isn’t great value. Its cheapest tariff is £15 per month on a two-year deal, whereas our best-value network, Lebara, will offer you a decent dollop of data for £4.50 per month. However, at the top end, O2’s £21 per month fee for unlimited data is up there with the best, although be aware that annual price increases are baked into the contract.

Take care if you’re planning to buy a phone and SIM together. When I priced up a deal for an iPhone 17 Pro and a 50GB monthly contract, the cheapest I could get the airtime plan was £30 per month (O2 prices the phone and airtime separately). If you buy a SIM-only 50GB plan from O2, you can get it for half that price.

It seems this is because O2 offers different tiers of 50GB plan, with the “Plus” tariff offered with the iPhone, including benefits such as data rollover, extended roaming and more. However, these benefits don’t seem worth double the cost, in my view, so you may be better off buying a phone and airtime separately.

Speed

Score: 3.5/5

The O2 customers we surveyed seemed largely content with the performance of the network, with 73 per cent satisfied with the data speeds on offer. As noted previously, award winners Tesco Mobile and Giffgaff also piggyback on O2, and their customers were also happy with the speeds (both registered 89 per cent satisfaction), which is a good sign.

Reliability

Score: 4/5

Reliability appears to be solid with O2, with 84 per cent of the customers we surveyed satisfied with the reliability of the network. Again, high scores from the customers of Tesco Mobile and Giffgaff (93 per cent and 95 per cent) boost confidence levels. Text and voice reliability is particularly strong, with 95 per cent of O2 customers happy. The best scores of any network on test.

Customer service

Score: 3/5

Customer service scores are a drag on O2’s overall performance. A middling 63 per cent of customers said they were happy with how easy it is to reach O2’s customer service team, while 62 per cent were satisfied with the quality of support. Tesco Mobile was the standout leader for customer service, with scores of over 90 per cent on both of those metrics.

Roaming

Score: 3.5/5

You need to check carefully with O2’s roaming offering, as it varies depending on which tariff you’ve chosen. The standard ‘Classic’ plans that are offered on a SIM-only basis include EU roaming, but up to a limit of 25GB per month. The more expensive ‘Plus’ tariffs include roaming in 75 countries, including the USA, while the top-tier ‘Ultimate’ tariffs boost the number of roaming countries to 123. Check the lists of supported countries carefully before you travel.

In our survey, 73 per cent of O2 customers were satisfied with the value of the roaming deals. Again, this is middle of the pack.