Use this section to check coverage, understand calling features, switch network safely and diagnose signal or data problems without guessing.
A mobile service is a chain: the phone, its software, the SIM or eSIM, the account, the operator’s network and the local radio signal all have to work together. A coverage map can show predicted service, but it cannot guarantee what happens inside one particular room or on one particular handset.
Choose the task you need to complete
| Your task | Start with | What to verify |
|---|---|---|
| Check a new network | Network Coverage & Signal | Indoor and outdoor coverage, a real SIM test and Wi‑Fi Calling |
| Keep your number | Network Switching & Porting | PAC, transfer date, account access and final billing |
| Improve calls indoors | Wi‑Fi Calling | Device, network and plan support for the exact line |
| Check modern voice support | VoLTE & Voice Services | 4G Calling support after the UK 3G switch-off |
| Understand 4G or 5G | 4G & 5G | Coverage, battery use, device bands and actual benefit |
| Fix slow data | Mobile Data Speed & Performance | Signal quality, congestion, allowance, settings and a controlled speed test |
| Share your connection | Tethering & Personal Hotspot | Plan rules, security, data use and power |
Compatibility comes before settings
Do not treat a feature label as proof that it will work. A phone may support 4G, 5G, VoLTE or Wi‑Fi Calling in hardware but still lack the correct regional firmware, operator profile or plan support. Imported and older devices deserve particular care.
A safe troubleshooting order
- Check the operator’s live status page and Ofcom’s predicted coverage.
- Confirm that the problem affects one place, one phone, one SIM or every service.
- Restart the phone and install current system and carrier updates.
- Check that the correct line is enabled and selected for calls and mobile data.
- Test with an ordinary call, a text and a small data task. Never call 999 or 112 for a test.
- Only then consider a network-settings reset or contact the provider with exact evidence.
What this site will not promise
No map, logo or generic compatibility list can guarantee indoor service. Provider features and MVNO support also change. The practical standard is always the same: check the exact device, network, plan and location, then verify the result before you depend on it.
How to use this section without over-troubleshooting
Start with the narrowest guide that matches the symptom. A phone that has signal but slow data needs a different check from a phone showing “No Service”; a delayed number port is not repaired by changing radio settings. Record the original state before each change and make one change at a time, so you can tell what actually solved the problem and roll back anything that made it worse.
The evidence worth recording
Start with the symptom and location, not with a reset. A coverage problem in one building, a delayed number port and a line that has signal but no data require different evidence and different support teams. The section is most useful when the reader records the original state, changes one variable at a time and verifies the result with an ordinary call, an SMS and a small data task.
- Check live network status before changing the phone.
- Compare another phone or SIM only when it isolates one variable.
- Keep a fallback connection before resetting, porting or replacing a working line.
Start with the layer that is actually failing
Mobile problems are easier to solve when coverage, voice service, data performance, the tariff and the phone are checked separately. This section moves from location and network capability to settings and account-side faults.
- Coverage and signal: Use Network Coverage & Signal for address checks, indoor dead spots, building materials and reporting a persistent local problem.
- Calls over modern networks: Use Wi-Fi Calling and VoLTE & Voice Services when calls fail indoors, during the 3G switch-off or on a phone that still has working data.
- 4G and 5G: Use 4G & 5G for compatibility, coverage transitions, 5G Standalone and the effect of retiring older network layers.
- Changing provider or number: Use Network Switching & Porting for PAC, STAC, PAYG/monthly migrations and delayed ports.
- Data and hotspot use: Use Mobile Data Speed & Performance and Tethering & Personal Hotspot for slow data, allowances, real-world speed and backup internet.
- Choosing a connection type: Use Network Types & Connection Options for MVNO, SIM-only, PAYG, monthly and data-only decisions.
What a complete answer looks like
A network decision is complete when the exact handset and tariff work in the places that matter, ordinary calls and data have been tested, and the reader understands whether the remaining limitation belongs to coverage, the account, the device or an application.
