Begin with the coverage description
Read whether the provider’s map describes outdoor, indoor or predicted coverage. A postcode can cover several buildings and environments. Walls, insulation, windows, hills and the position of the phone can influence the result.
Use ordinary tasks
Try a voice call, a message, a webpage and a short video call in the places you actually use the phone. Test at a quiet time and at a busy time. A single download-speed result does not capture unreliable incoming calls or repeated disconnections.
Compare carefully
Keep the device and task the same where possible. Different phones may support different bands and voice features. Check the official status page so that a known temporary interruption does not become your assumption about normal performance.
Write a useful conclusion
Say what worked, where and when. Avoid describing one provider as universally best from a small personal test. If Wi-Fi calling is important, verify eligibility and test it too; it depends on a working local internet connection.
Source notes
Confirm the current detail with the official provider. Links are references, not partnerships.
Ofcom consumer information ↗