Making Voice over WiFi (VoWiFi) calls when there is wifi but _no cellular service_ is not possible. Attempting calls just immediately hangs up in the Phone Dialer app with the message `connect to a wireless network to make a call`. Receiving WiFi calls does work correctly. To confirm you are configured correctly with your carrier to allow VoWifi do the following: `Dial *#*#4636#*#* > Phone Information > 3 dots > IMS Service Status > Voice over WiFi` and confirm it shows **_`Available`_**. To test a VoWiFi _only_ call, in Network settings, go to `Settings > Network & internet > SIMs > (your) SIM > Wi-Fi calling > Calling preference` and set to `Wi-Fi only`. If there is still cellular connection, making a call will show the wifi symbol at the top of the dialer. But when enabling Airplane Mode (it isn't easy for me to leave cellular coverage land to test otherwise :-), the Dialer (or other dialer apps) show the message to `connect to a wireless network to make a call` and immediately close. I did try with the same results with 2 other Phone Dialer apps (including Google Phone app). I believe this to be a LineageOS bug introduced _after LOS 20_, but there isn't much (any) traction on their issue trackers: https://gitlab.com/LineageOS/issues/android/-/issues/7262 https://gitlab.com/LineageOS/issues/android/-/issues/7297