Three MVNOs use Three's network in the UK: Honest Mobile, iD Mobile, and Smarty. All three offer the same 4G and 5G coverage as Three itself, with different contract terms, roaming policies, and pricing. Since the VodafoneThree merger completed in May 2025, customers of all three MVNOs are also gradually gaining access to Vodafone's masts through a network-sharing arrangement, which expands coverage in many areas. This guide explains what each MVNO offers and what the merger means in practice. Verified in May 2026.
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Reviewed by: Phil Brown, founder of SIM Only Finder. Phil previously worked in UK mobile retail at Three UK, advising customers on SIM plans, contracts, and network choices. He has spent over a decade running consumer comparison platforms and reviews networks and SIM-only deals based on that hands-on industry background. About the author
Last reviewed: May 2026. Updated regularly to reflect current plan pricing, network changes, and roaming policies.
How we put this guide together
To put this guide together, we reviewed the three MVNOs currently running on Three's network in May 2026, checking contract terms, 5G access, roaming policies, and price rise terms directly against each network's published terms. We also drew on our broader experience reviewing UK SIM-only networks and tracking how MVNO arrangements have changed over time, including the ongoing integration following the VodafoneThree merger. Coverage reliability assessments reference the most recent RootMetrics UK RootScore Report and Ofcom Connected Nations data.
What "uses Three's network" actually means
Honest Mobile, iD Mobile, and Smarty are MVNOs (mobile virtual network operators). They do not own mast infrastructure. Instead, they buy wholesale access from Three and resell SIM plans under their own brands. The signal you receive on your phone is the same Three signal that a Three direct customer would get in the same location, with one important addition that has changed since the VodafoneThree merger, covered in the next section.
4G and 5G coverage on Three is identical to Three on all three MVNOs. What changes between the host network and its MVNOs is the contract terms, the extras, and the price. Three supports Wi-Fi Calling and 4G Calling, also known as VoLTE, which routes voice calls over the 4G network rather than older 2G or 3G connections to give faster call setup and better audio quality. This matters because Three switched off its 3G network in 2024, ahead of the rest of the industry. Support for Wi-Fi Calling and 4G Calling on each MVNO varies by plan and handset, so it is worth checking your specific phone model against the network's supported devices page before switching.
Three's network has historically been a strong choice for 5G data speeds. According to the Opensignal January 2026 UK Mobile Network Experience Report, Three recorded the highest 5G download speeds of any UK network at an average of 187 Mbps, and the highest 5G upload speeds at 20.2 Mbps. The trade-off is geographic coverage: Ofcom's Connected Nations 2025 report places Three at 10% to 23% of UK landmass for 5G geographic coverage, behind both EE and O2. The post-merger network sharing with Vodafone helps close this gap.
What the VodafoneThree merger means for you
Vodafone UK and Three UK completed their merger on 31 May 2025, forming VodafoneThree. The combined company is the UK's largest mobile network by subscriber count, with over 27 million customers across its brands. The two networks continue to operate under separate brand names, and your Three SIM still says "Three" on your phone. What has changed is what happens underneath.
VodafoneThree is gradually rolling out a technology called Multi-Operator Core Network (MOCN), which allows Three customers to connect to Vodafone masts and vice versa, automatically selecting the strongest signal. VodafoneThree confirmed around 500 MOCN-enabled mast sites in August 2025, with a target of around 10,000 sites enabled by March 2026 and full nationwide rollout expected by 2033. The MOCN benefit was first made available to VodafoneThree-owned brands (Vodafone, Three, VOXI, Smarty, and Talkmobile), and third-party MVNOs including iD Mobile and Honest Mobile have since been added on a rolling basis.
In practice this means that a Three, iD Mobile, Honest Mobile, or Smarty customer in an MOCN-enabled area gets the choice of two networks instead of one, which expands coverage in places where one network had a weak signal. Opensignal's October 2025 analysis projects that once integration is complete, Three customers will see around a 13% improvement in coverage experience, while Vodafone customers will see around a 7% improvement, on average. Some of those gains are already showing in current data, including an 8% increase in download speeds on Three between Q2 and Q3 2025. Your phone makes the switching decision automatically and there is nothing you need to do. 5G Standalone (5G SA) is not yet part of MOCN, so any 5G SA benefits are still tied to your home network.
Honest Mobile
Honest Mobile is a small Three-based MVNO that has built a distinctive position around ethics and customer loyalty. The network is a certified B Corporation, carbon negative (offsetting more emissions than it produces), and a member of 1% for the Planet, donating 1% of revenue to environmental causes. The customer-facing differentiator is the loyalty discount: rather than raising prices over time, Honest Mobile drops your monthly bill by 0.41% every month you stay, accumulating to a maximum 30% discount.
Plans are SIM-only on 30-day rolling or 12-month terms, with three data tiers: 4GB, 10GB, and unlimited. All plans include unlimited UK minutes and texts, 5G, Wi-Fi Calling, and EU roaming. The roaming policy is unusual: five free days per trip with up to 20GB of data, after which there is a £2 per day charge. A 60-day annual fair usage limit applies to total roaming. eSIM is supported.
Honest Mobile also offers an unusual second product called Smart SIM, an additional eSIM that connects to all four UK networks (EE, O2, Three, and Vodafone) for over 500 supported apps and includes free roaming in more than 180 countries. It is a backup data-only SIM rather than a replacement for the main plan, and works alongside your existing SIM. Smart SIM costs £10 per month or £45 per year, and is most useful for travellers or anyone with patchy coverage at home. We tested the Smart SIM in the UK and abroad in our Honest Mobile Smart SIM review.
Customer service is app-based with an average response time of around 35 seconds. The network has a Trustpilot rating of 4.7 out of 5 from over 3,000 reviews. Honest Mobile is not the cheapest Three MVNO, with plans starting from around £12 per month for 4GB, but the loyalty discount and Smart SIM option make the longer-term value competitive.
Best for: Customers who want Three coverage with strong ethical credentials, a bill that drops rather than rises over time, and the optional Smart SIM backup for travel or areas with weak signal.
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iD Mobile
iD Mobile is the second-largest Three MVNO and is owned by Currys, the UK technology retailer. The network has built a reputation around value and useful features, particularly data rollover and inclusive international roaming. SIM-only plans are available on 30-day rolling, 12-month, or 24-month terms.
Every iD Mobile plan includes data rollover, where unused data from one month automatically rolls into the next month and is used first. Rollover data expires after one month, so you cannot accumulate it long-term, but it does give you a buffer. EU roaming is included in 50 destinations including some outside Europe, with a 30GB fair usage cap. iD Mobile also offers paid roaming passes for popular non-EU destinations such as the USA, Australia, India, and Turkey, which is unusual for a budget MVNO. 5G is included at no extra cost, and Wi-Fi Calling is supported on compatible handsets.
iD Mobile has committed to no annual price rises on its SIM-only plans, which is significant on its 12 and 24-month contracts. Note that this commitment applies only to SIM-only, not to handset contracts where annual increases still apply. A credit check is required for Pay Monthly and longer-term SIM-only plans. According to Ofcom's 2025 Pricing and Consumer Engagement report, iD Mobile offered the lowest-priced Pay Monthly SIM-only tariffs with 10GB to 100GB of inclusive data every month from March 2023 to September 2025.
Spending caps can be set in £1 increments between £0 and £25, which is more flexible than most networks. Customer service is handled through the iD Mobile app, online chat, and phone. There are no physical iD Mobile stores, but the Currys ownership means in-person support is available at any Currys branch.
Best for: Value-focused customers who want Three coverage with data rollover, flexible spending caps, and a price-rise guarantee on SIM-only plans. Also a strong choice for occasional non-EU travellers who want predictable roaming costs.
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Smarty
Smarty is a Three-owned MVNO (now part of VodafoneThree) and the most flexible of the three. All Smarty plans run on 30-day rolling contracts only, with no longer-term tie-ins. There is no credit check on any plan. The network is positioned as Three's budget-friendly arm and is consistently among the cheapest Three MVNOs, with plans starting from around £6 per month.
5G is included on all plans at no extra cost, and the network supports eSIMs. All plans include unlimited UK calls and texts, with data allowances ranging from 4GB to unlimited. EU roaming is included with a 12GB fair usage cap. Smarty has committed to no annual price rises on its current plans, and because all plans are 30-day rolling, customers are free to leave if pricing ever changes.
Smarty has two features worth knowing about. The first is data discount: on selected plans, any unused data at the end of the month is refunded as a £1-per-GB credit against the following month's bill. The second is Group Plans, which give a 10% discount on every SIM when up to eight SIMs are linked under one account, useful for families or households. Customer service is handled through web chat only (there is no phone support) between 8am and 8pm daily.
Because Smarty is owned by VodafoneThree, it was among the first networks to benefit from MOCN access when the merger completed, meaning Smarty customers in MOCN-enabled areas have been able to connect to Vodafone masts as well as Three masts since June 2025.
Best for: Cost-conscious customers who want Three coverage on a 30-day rolling plan with no credit check, the option of data discounts, and the longest track record of access to the post-merger MOCN coverage benefits.
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How to choose between Three and a Three MVNO
Going direct to Three gives you access to the Three+ Rewards loyalty programme, the full range of Three's Pay Monthly handset deals, and the network's wider contract structures including custom term lengths. Three is also the UK leader for 5G download speeds, with an Opensignal average of 187 Mbps in January 2026.
Three has applied mid-contract price rises in April 2026. Customers who signed up after November 2025 will see fixed increases based on their data allowance: £1.80 per month for plans of 4GB or below, £1.90 per month for plans between 5GB and 99GB, and £2.30 per month for plans of 100GB and above. Customers on older contracts face an increase of CPI plus 3.9%, which works out at 7.3% for April 2026 based on the December 2025 CPI rate.
Going with an MVNO almost always gets you a lower monthly price for equivalent data and minutes. Smarty is usually the cheapest and most flexible. iD Mobile is the best for data rollover and a price-rise commitment on SIM-only plans. Honest Mobile is the right answer if you value the ethical positioning and the unique Smart SIM backup product. Coverage is identical on the underlying Three network across all four options, with all MVNOs and Three customers now sharing in the MOCN-enabled access to Vodafone masts. The choice comes down to contract terms, extras, and price. For details on how each network's price rise terms compare across the wider market, see our guide to SIM-only mid-contract price rises.
Conclusion
The three MVNOs running on Three's network in May 2026 are Honest Mobile, iD Mobile, and Smarty. All three offer the same 4G and 5G coverage as Three itself, with different contract terms, roaming policies, and pricing. Smarty is the cheapest and most flexible. iD Mobile is the best for data rollover and predictable pricing on SIM-only plans. Honest Mobile is the best for ethical credentials and the Smart SIM backup product. The VodafoneThree merger means all four networks (including Three itself) are gradually gaining MOCN access to Vodafone masts, with VodafoneThree targeting around 10,000 enabled sites by March 2026 and full nationwide rollout expected by 2033.
How to switch to a Three-based network
To switch from your current network to Honest Mobile, iD Mobile, or Smarty while keeping your existing phone number, you need a PAC code from your current provider. Text PAC to 65075 from the number you want to transfer and your network will reply with the code within a minute. The code is valid for 30 days. Give it to your new network when you sign up, and your number will transfer within one working day. For network-specific switching steps, see our guides for switching to iD Mobile, switching to Smarty, or switching to Three. For Honest Mobile, contact the network directly through their app or online chat to start a number transfer.
If you do not need to keep your number, you can simply order a new SIM from the network of your choice and start using it straight away.
Editorial policy
This guide is produced by the SIM Only Finder editorial team to help readers compare the MVNOs running on Three's network across UK networks. Network terms, pricing, and feature availability are checked regularly and updated to reflect current offers. Always confirm current terms directly with the network before signing up.
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