If calls over Wi-Fi is activated on your Huawei device, you can, depending on signal strenght, make calls within a Wi-Fi network.

Note: If you activate Wi-Fi calling for the first time, you will be notified that it is not possible to make emergency calls using Wi-Fi calling.

Android 10 | EMUI 10.0
Wi-Fi calling -  Open the  Phone app
Wi-Fi calling -  Open the  menu
Wi-Fi calling -  Open the  settings
Wi-Fi calling -  Tap on  Wi-Fi Calling
Wi-Fi calling -  Activate  Wi-Fi Calling
Wi-Fi calling -  Confirm with  Enable
  1. Open the Phone app
  2. Open the menu
  3. Open the settings
  4. Tap on Wi-Fi Calling
  5. Activate Wi-Fi Calling
  6. Confirm with Enable

Huawei Instructions