Calls and messages on a Galaxy S20 depend on the SIM, the network and a handful of phone settings, and when calls drop, texts fail or the phone shows no signal, the fix is normally in those settings. The S20 supports 4G, 5G on the 5G models and Wi-Fi calling, so start with Settings, Connections, Mobile networks and check the network mode. Many carriers have retired older 3G networks, and a phone set to an old mode or with an old carrier profile may lose calls; choose the automatic 5G, LTE or 3G option. Confirm that VoLTE and Wi-Fi calling are on in Settings, Connections, because carriers that need them will drop calls without. Restart the phone and toggle Airplane mode.
The checks in more detail
If only texts fail, check which messaging app is the default, and whether the phone's settings let RCS chat features work; if you have moved from an iPhone, make sure you have turned off iMessage for your number, or texts may not arrive. Clear the cache of the Messages app, and check that blocked numbers and spam filters are not catching the sender.
For a group message that fails, switch between MMS and RCS as the carrier supports. Check that the SIM is seated well, and try it in another phone to see whether it is the SIM or the S20. If calls break up in one place, the network may be weak there, and Wi-Fi calling is the answer. If echo or one-way audio occurs, test the phone's earpiece and microphone on speaker, clean the grilles and check the case.
Update the software, though the S20 has few updates left, and ask the carrier to refresh the line: they can resend the network settings and check that the phone's IMEI is not blocked. Reset mobile network settings from Settings, General management, Reset, and then test. A phone that no longer finds any network with a good SIM may have a hardware fault. Keep emergency calling in mind: if the phone cannot make calls, use another phone for emergencies. Because the S20 is old, its radio software may not know the newest features of the networks that carriers now run, so a carrier that has switched off its older networks can leave the phone with patchy service in some places.
Ask the carrier whether the S20 is still listed as supported and whether a newer SIM is needed, since an old SIM can fail to register on a modern network, and a replacement is usually free. Use the carrier's own app or website to check that the line is provisioned for VoLTE and Wi-Fi calling, because a line set up years ago on an older plan may lack them. If calls echo or cut out only on speakerphone, test the microphone and speaker in the Samsung Members diagnostics, and clean the grilles. When a message fails to send with a red mark, tap it for the reason, such as a blocked number or no data, and use that to decide the next step.
Differential
Likely causes of “Samsung Galaxy S20 family cannot make calls or send messages”, and how to tell them apart
- 1
An old network mode
What separates it Calls drop where the network changed
How to confirm Choose the automatic mode
- 2
VoLTE or Wi-Fi calling off
What separates it Calls fail
How to confirm Turn them on
- 3
iMessage still registered
What separates it Texts from iPhones do not arrive
How to confirm Turn off iMessage for the number
- 4
A SIM that is loose or faulty
What separates it No service
How to confirm Test the SIM in another phone
- 5
A weak signal location
What separates it Calls break up in one place
How to confirm Use Wi-Fi calling
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether calls, texts or both fail
- The network mode
- Whether VoLTE is on
- Whether the SIM works elsewhere
Try in this order
0 of 6 completedRestart and toggle Airplane mode
ReversibleFirst.
Check the network mode
ReversibleAutomatic.
Turn on VoLTE and Wi-Fi calling
ReversibleIn Connections.
Clear the Messages cache
ReversibleAnd check the default app.
Test the SIM
ReversibleIn another phone.
Reset mobile network settings
ReversibleLast.
Model-specific
What is true of this model and not of its siblings
- VoLTE
- Many carriers need it.
- iMessage
- Turn it off when leaving iPhone.
Stop boundary
When this stops being a self-service repair
- !If no network is found with a good SIM, contact Samsung or the carrier
- !If a carrier blocks the IMEI, contact the carrier
- !Use another phone for emergencies
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why do calls drop on my S20?+
An old network mode or VoLTE off.
Why do iPhone texts not arrive?+
iMessage may still hold the number.
Does Wi-Fi calling help?+
Yes, in weak areas.
Can the carrier help?+
They can resend settings and check the IMEI.