Diagnose poor calls by comparing location, network, SIM and device before resetting or replacing anything.
First classify the symptom
| Symptom | Useful first check |
|---|---|
| Calls break up only in one place | Coverage, building materials and local congestion. |
| Every call is quiet or distorted | Speaker, microphone, case, debris or accessibility settings. |
| Data works but calls fail | VoLTE/4G Calling provisioning and phone compatibility. |
| Only one contact sounds poor | Their phone, network or calling app may be involved. |
| Calls fail after a SIM/network change | Account activation, carrier settings and porting status. |
A controlled comparison
- Remove a case only if it blocks a microphone or speaker opening.
- Make an ordinary call in a second location.
- Try speakerphone and a headset to isolate the audio path.
- Check whether the phone stays on 4G/5G during the call.
- Restart and install current system/carrier updates.
- If possible, test the SIM in another supported phone or another SIM in this phone.
Evidence for the network
Record date, time, postcode, indoor/outdoor position, phone model, software, signal type and whether multiple numbers were affected. “Bad signal everywhere” is much harder to investigate than a repeatable location and symptom.
Do not use emergency numbers as a test
Use ordinary calls or the operator’s diagnostic route. Call 999 or 112 only in a real emergency.
Separate receive and transmit problems
If you hear the other person clearly but they cannot hear you, focus on the microphone path, case, Bluetooth route and upload quality. If the reverse happens, check speaker, earpiece and incoming audio. If both directions break at the same time in one location, radio coverage or congestion becomes more likely.
Bluetooth accessories can remain selected unexpectedly. Repeat one call with Bluetooth off before blaming the phone’s internal audio hardware.
What to confirm before the old setup is removed
Use the direction and location of the fault to isolate it. If only one person cannot hear, test microphone, earpiece, speakerphone and Bluetooth separately. If both directions fail only in one area or time period, record coverage and congestion evidence before resetting the device.
- Compare Wi‑Fi Calling and mobile calling.
- Test another ordinary number.
- Escalate with timestamps and exact symptoms.
Official sources
Facts checked: 25 July 2026. Coverage, device support, plan rules and menu paths can change. Recheck your exact phone, software version, network and plan before acting.
