SWITCHING

3G Switch-Off UK 2026: My Phone Stopped Working — The Complete 4G Calling & SIM Checklist for Every Network

A step-by-step troubleshooting guide to get your calls, texts and data back on every UK network after 3G shutdown.

Updated 2026-09-15 · 7 min read · NetScan UK

KEY TAKEAWAYS

If your phone stopped working after the 3G switch-off, the cause is almost always a lack of VoLTE support, an outdated SIM card, or a disabled 4G Calling setting — check all three before buying a new device.
Every UK network (EE, Vodafone, O2, Three) and their MVNOs maintain specific VoLTE-compatible device lists — your exact model number matters, not just the brand.
Replacing an old SIM with a free 4G-ready USIM from your network is the quickest, zero-cost fix and should be your first step.
Three has the thinnest rural and indoor 4G footprint; if losing 3G has left you with no signal, switching to a network with better coverage at your postcode may be the real solution.
Run a free postcode check at netscanai.co.uk/#scan to see which of the four networks actually delivers the strongest 4G at your address before committing to a new plan.
The 2G switch-off is coming next — buying a VoLTE- and VoWiFi-capable handset now future-proofs you against further network retirements.

If your phone stopped working after the 3G switch-off, you are far from alone. UK networks are progressively shutting down their 3G infrastructure to free up spectrum for 4G and 5G, and handsets that relied on 3G for voice calls — even those that could browse on 4G — are suddenly unable to make or receive calls. The problem is not always the phone itself: it can be an old SIM card, a missing network setting, or a handset that simply does not support Voice over LTE (VoLTE). This guide walks you through every scenario, network by network, so you can diagnose the issue and fix it in minutes rather than hours on hold to customer service.

The 3G shutdown matters because, historically, many 4G phones still fell back to the 3G layer to place traditional voice calls. With that layer gone, your device must support 4G calling — commonly branded as VoLTE or, on EE, as "WiFi Calling & 4G Calling" — otherwise it has no way to set up a voice circuit. Texts sent via the old 2G/3G signalling path can also be affected, which is why some users report being able to browse the web on 4G yet finding calls and SMS completely broken. Understanding this dual nature of the problem is the first step to solving it.

Each of the four UK mobile network operators — EE (owned by BT), Vodafone, Three, and O2 (part of Virgin Media O2) — is on its own timeline and maintains its own list of VoLTE-compatible handsets. The dozens of MVNOs that ride on those networks, such as giffgaff and Tesco Mobile on O2, SMARTY and iD Mobile on Three, VOXI and Lebara on Vodafone, and 1pMobile on EE, inherit the host network's VoLTE support but sometimes have additional SIM or provisioning requirements. We cover every permutation below so you can pinpoint your exact situation.

Before you spend money on a new phone or plan, we strongly recommend running a free postcode check using NetScan UK's coverage scanner at netscanai.co.uk/#scan. It ranks all four networks for your specific address using Ofcom premises-level data, so you can see whether your area even has robust 4G from your current operator — and whether switching network might solve the problem more cheaply than buying a new handset. Pair that with each operator's own coverage map for a belt-and-braces view of what signal you can realistically expect indoors and out.

Why your phone stopped working after the 3G switch-off

The core issue is deceptively simple. When a network turns off its 3G layer, any device that used 3G for voice calls — a technology called Circuit-Switched Fallback (CSFB) — loses the ability to dial out or receive calls. Even a phone that happily shows "4G" in its status bar may have been silently dropping to 3G every time you hit the green call button. With the 3G mast no longer transmitting, that fallback path vanishes and calls fail instantly. Data sessions on 4G may still work perfectly, which is why the fault feels so confusing.

There are three main reasons a phone ends up in this state. First, the handset hardware or software simply does not support VoLTE on your network — this is common with budget Android devices imported from other markets and with older flagships launched before VoLTE was widely rolled out. Second, the SIM card pre-dates 4G provisioning; some SIMs issued years ago lack the applets needed for VoLTE authentication. Third, the VoLTE toggle may be present but switched off in your phone's settings, or the network has not yet enabled the feature on your account. Each cause has a different fix, which is why a methodical checklist matters.

The network-by-network VoLTE and 2G/3G status checklist

EE was the first UK network to begin retiring 3G sites and has been actively migrating customers to VoLTE for several years. If your phone stopped working after the 3G switch-off on EE, check that your device appears on EE's official VoLTE-compatible list (available on their support pages) and that 4G Calling is toggled on in your phone's mobile-network settings. EE has the widest geographic and rural coverage of any UK network and serves as the Emergency Services Network backbone, so 4G signal availability is less likely to be the issue — but an old SIM may still need swapping. EE stores and customer service will replace it free of charge.

Vodafone has similarly been transitioning users to VoLTE and has published a compatibility checker on its website. MVNOs on Vodafone — VOXI and Lebara — inherit Vodafone's VoLTE-supported device list, but you may need to contact their support to ensure the feature is activated on your account. Vodafone's 4G coverage is generally strong in urban and suburban areas, though it does not match EE's rural reach. If you are in a marginal signal area, enabling Wi-Fi Calling alongside VoLTE can provide a valuable fallback for indoor use.

O2 (Virgin Media O2) presents a particular pain point because VoLTE is not supported on every device that O2 sells or has sold. If you find VoLTE not supported on O2 for your handset, your only options are to upgrade to a compatible device or switch to a network whose VoLTE whitelist includes your phone. O2 is also in the process of planning its 2G switch-off timeline — the 2G switch-off on O2 is a separate but related event that will further narrow the technologies available for older handsets. giffgaff and Tesco Mobile, both running on O2's infrastructure, follow the same VoLTE device list. Do you need a new SIM for 4G on O2? If your SIM was issued before 2015, the answer is very likely yes — request a free replacement through the My O2 app or a giffgaff/Tesco Mobile account page.

Three is the only UK network that never operated a 2G layer, so it has always been 3G-and-above. Its 3G switch-off therefore has an outsized impact: once 3G goes, Three customers must have VoLTE or they have nothing at all. Three's VoLTE rollout has been somewhat narrower in device support compared with EE, so check their approved list carefully. MVNOs SMARTY and iD Mobile ride on Three's masts and share the same VoLTE requirements. Bear in mind that Three has the thinnest rural and indoor footprint of the four UK networks, so if your postcode already showed marginal Three coverage on 3G, losing that layer may effectively leave you with no usable signal. Running a postcode check at netscanai.co.uk/#scan will show whether another network offers stronger 4G at your location.

Do you need a new SIM for 4G? How to tell and what to do

One of the most common — and most easily fixed — causes of a phone stopping working after the 3G switch-off is an outdated SIM card. 4G and VoLTE require a USIM (Universal SIM) with updated network applets. SIM cards issued before roughly 2014–2015 frequently lack these applets, which means your phone may connect to 4G for data but cannot authenticate VoLTE sessions. The symptom is identical to having a non-VoLTE handset: data works, calls do not.

The quickest way to find out whether you need a new SIM for 4G is to check the ICCID number printed on the SIM (or in your phone's SIM status menu). Each network publishes guidance on which ICCID prefixes are 4G-ready. If yours is not, every UK network and MVNO will send you a replacement SIM — or eSIM where supported — free of charge. On giffgaff, you can order one through the app; on SMARTY, it arrives within a couple of days; on 1pMobile, you can request one via their website. Swapping the SIM takes seconds and preserves your number, so there is no reason not to try this step first before buying a new phone.

Handset compatibility: is your phone VoLTE-ready?

If a fresh SIM does not fix the problem, the handset itself is the next suspect. VoLTE support is not purely a hardware question — it also depends on the phone manufacturer certifying VoLTE with each specific UK network. A Samsung Galaxy model might support VoLTE on EE but not on Three, for example. Apple iPhones from the iPhone 6 onward generally support VoLTE across all four UK networks, but Android support is far more fragmented. Always cross-reference your exact model number (not just the name) against the network's published compatibility list.

If your phone is confirmed as unsupported, you face a choice: buy a VoLTE-capable handset or switch to a network that does whitelist your device. Before spending money, check the budget end of the market too — check the exact model against your network's VoLTE list, as support is model-specific. Pairing a SIM-free phone with an MVNO SIM-only plan is often a cost-effective route; check each provider's own site for today's prices.

Switching network: when it is the smartest fix

Sometimes the 3G switch-off simply exposes a deeper problem — that your current network's 4G coverage at your postcode was always propped up by 3G infill. With the 3G layer gone, you may find indoor signal has evaporated entirely. In rural areas, this is especially common on Three, which has the smallest geographic footprint among the four UK MNOs. If that is your situation, no amount of SIM-swapping or VoLTE toggling will help; you need a network with stronger 4G (or 5G) at your location.

Start with a postcode check at netscanai.co.uk/#scan to see how EE, Vodafone, O2 and Three rank for your address based on Ofcom Connected Nations data. Remember that 'population coverage' figures quoted in marketing refer to where people live on average, not to your specific house — geographic coverage and indoor penetration vary enormously. EE typically leads in rural reach, with Vodafone and O2 generally next, and Three trailing in the countryside. Once you have identified the strongest network at your postcode, pick an MVNO on that host network for the best value.

For those who want unlimited data without committing to a big-network contract, compare the unlimited SIM-only plans from MVNOs on the network that covers you, on the providers' own sites — prices change without notice. EE, O2, Three and Vodafone also sell their own direct plans. Switching is now straightforward thanks to Ofcom's PAC / STAC text-to-switch system and should complete within one working day.

Future-proofing: the 2G switch-off and what comes next

The 3G switch-off is not the end of the story. Networks are also eyeing the eventual retirement of 2G, which still underpins some IoT devices, older alarms, and basic "brick" phones. The 2G switch-off on O2 and other networks has been discussed but no universal UK-wide deadline has been confirmed at the time of writing. When it happens, any device that lacks VoLTE — including many feature phones that currently fall back to 2G for calls — will stop working entirely. If you are buying a new phone today, ensuring it supports VoLTE (and ideally VoWiFi / Wi-Fi Calling) across multiple UK networks is the single best way to future-proof yourself.

It is also worth keeping eSIM capability in mind. An eSIM lets you switch networks in minutes without waiting for a physical card in the post, which can be invaluable if a network's coverage changes or a better deal appears. Most mid-range and flagship phones from 2022 onward support eSIM, and an increasing number of MVNOs — including giffgaff and VOXI — now offer eSIM activation. Combined with a VoLTE-ready handset and a verified postcode check, you will be well prepared no matter which legacy technology is retired next.

Check the best network for your postcode

Don't guess from a national average — see EE, Vodafone, O2 and Three ranked for your exact area in seconds.

Scan my postcode →

Frequently Asked Questions

Why has my phone stopped working after the 3G switch-off?

Your phone almost certainly relied on 3G to place voice calls via a process called Circuit-Switched Fallback. With 3G gone, it needs VoLTE (Voice over LTE) to make calls over 4G instead. If your handset, SIM card or account settings do not support VoLTE, calls and sometimes texts will fail even though mobile data may still work. Check your network's VoLTE device list, request a replacement SIM if yours pre-dates 2015, and ensure 4G Calling is toggled on in your phone's settings.

Do I need a new SIM for 4G?

Possibly. SIM cards issued before around 2014–2015 may lack the USIM applets required for VoLTE authentication. Your phone might connect to 4G for data but still be unable to place calls. Every UK network and MVNO will send a free replacement SIM or eSIM — this is one of the fastest fixes available and should be tried before purchasing a new handset.

VoLTE is not supported on O2 for my phone — what are my options?

O2's VoLTE-compatible device list is more restrictive than some rival networks, so certain handsets that work fine on EE or Vodafone may not support VoLTE on O2. Your choices are to upgrade to a handset that O2 does support, or to switch to a different network (or its MVNOs) where your current phone is whitelisted. Check EE's, Vodafone's and Three's lists before spending money — your device may already be approved elsewhere.

Will the 2G switch-off on O2 affect me too?

The 2G switch-off on O2 has been discussed but no firm UK-wide date has been publicly confirmed at the time of writing. When it does happen, any device relying on 2G for calls — including many basic feature phones and some IoT/alarm devices — will stop working on O2 and its MVNOs (giffgaff, Tesco Mobile). Buying a VoLTE-capable phone now is the best way to stay ahead of this change.

I'm on giffgaff / SMARTY / VOXI / 1pMobile — does the 3G switch-off affect MVNOs?

Yes. MVNOs use the masts and spectrum of their host network, so they are subject to exactly the same 3G retirement schedule. giffgaff and Tesco Mobile ride on O2; SMARTY and iD Mobile on Three; VOXI and Lebara on Vodafone; and 1pMobile on EE. The VoLTE device list and SIM requirements of the host network apply in full, though you may need to contact your MVNO's support separately to ensure VoLTE is provisioned on your account.

How do I check which network has the best 4G coverage at my address?

Use NetScan UK's free postcode scanner at netscanai.co.uk/#scan, which ranks EE, Vodafone, O2 and Three for your specific address using Ofcom Connected Nations premises-level data. Supplement this with each operator's own coverage map for an indoor vs outdoor breakdown. Remember that headline 'population coverage' statistics do not reflect individual postcodes — especially in rural areas where geographic coverage varies enormously between networks.

Is switching network the only fix if my phone is not VoLTE-compatible?

Not necessarily. First, check whether a software update from your phone's manufacturer adds VoLTE support — some older models gained it through firmware updates. Second, verify whether the phone supports VoLTE on a different UK network; a device unsupported on O2 might work perfectly on EE. If neither applies, then a new handset is needed. Budget VoLTE-ready smartphones are available SIM-free, and pairing one with a cheap MVNO SIM-only deal keeps costs down.

What is the cheapest way to get back online after the 3G switch-off?

If your current phone supports VoLTE on at least one UK network, swapping to that network via a low-cost MVNO is the cheapest route. MVNOs such as 1pMobile (on EE) or SMARTY (on Three) sell low-cost SIM-only plans — check their own sites for today's prices. If you also need a new handset, buying SIM-free and adding one of these plans avoids lengthy contracts. Plan prices change often, so always check the latest figures before ordering.

Can Wi-Fi Calling help if 4G signal is weak after the 3G switch-off?

Yes. Wi-Fi Calling (VoWiFi) routes your calls over a broadband connection instead of the mobile network, which is a lifeline in buildings with thick walls or in rural areas with thin outdoor coverage. Most networks and MVNOs now support it on compatible handsets. Enable it in your phone's call settings alongside VoLTE. Note that Wi-Fi Calling still requires a VoLTE-capable device and a 4G-ready SIM, so the same checklist applies.

See each network's plans

Coverage first, price second — check your postcode above, then see what the network that actually reaches you is charging.

EE plans → Vodafone plans → O2 plans → Three plans →

Some links on this page are affiliate links. If you switch through one we may be paid a commission. It never changes which network we rank first - that comes from Ofcom coverage data alone.

Related guides