Most individuals have spent time in locations where the phone signal is either weak or nonexistent. Whether it is an underground cafe, lift, or a basement office, there are always a few places where there is no phone signal. This is where wi-fi calling comes handy. However, if you are facing Wi-Fi calling issues, then check out the solutions mentioned below.

Force Restart the Device and Insert the SIM Card Again into the Mobile

You should pursue the guidelines provided below:

Open the notification panel and press and hold the icon of Wi-Fi.
Thereafter, select the option of ‘Wi-Fi Preferences’ then launch the Advanced option.
You should turn off the Wi-Fi calling option and remove the SIM from the mobile.
Later, long-press the Power and Volume down keys until the mobile reboots.
Now, let go of the keys and if the ‘Maintenance Boot Mode’ screen pops up, choose the ‘Normal Mode’ or Reboot option.
You should insert the SIM again and turn on the option of Wi-Fi calling.
Remove the Data and Cache of the Google Fi Application

You should pursue the guidelines provided below:

Open the Mobile’s Settings and invoke the Application Manager.
You should locate and select the Google Fi Application.
Go to the Storage option and select it.
Choose the ‘Clear Cache; option and then select the Clear Data option.
Enable the Airplane Mode

You should pursue the guidelines provided below:

Firstly, pull down the notification panel to access the Quick Settings on the device.
After that, select the icon of the Airplane to turn on the Airplane Mode.
Then long-press the icon of Wi-Fi and link to the Wi-Fi connection.
Turn on Wi-Fi Network in the Wi-Fi Calling Settings

You should pursue the on-screen guidelines provided below:

Open the Settings and launch the Calling Plus option.
Thereafter, select the Wi-Fi Calling option.
You should turn on the Wi-Fi connection beneath the ‘WIFI Calling Networks’ option.
Updating the Carrier Services App

You should pursue the guidelines provided below:

Invoke the ‘Google Play Store’ app and select it Menu.
Then choose the ‘My Apps & Games’ option.
You should go to the tab of Installed and choose the ‘Carrier Services’ option.
Click on the button of Update and reboot the device once the updates are installed.
In case the solutions mentioned above do not work, then try to update the OS of your mobile device.

source :- https://dmogul.com/how-to-fix-wi-fi-calling-issues/