Open your phone’s Settings
Tap Cellular, Mobile Network, or Connections
Select Wi-Fi Calling
Turn off Wi-Fi Calling
On iPhone, go to Settings > Phone > Wi-Fi Calling, then turn it off
On Android, go to Settings > Network & Internet > Calls & SMS or Connections > Wi-Fi Calling, then turn it off
If needed, open your carrier app and disable Wi-Fi Calling there
Restart your phone if the setting does not turn off immediately