The Samsung device can also make calls via mobile data (VoLTE) as well as via Wi-Fi (VoIP) in addition to the normal mobile phone network. Samsung simply calls this "WiFi calling" on its smartphones. The function can be turned on or off via the phone settings.

Note: The network provider must support WiFi calling.

Android 10 (One UI 2.0)
Step 1:  Open the  Phone app
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  Wi-Fi Calling
Step 5:  Choose a  SIM card
Step 6:  Enable or disable  Wi-Fi Calling
  1. Open the Phone app
  2. Open the menu
  3. Open the Settings
  4. Tap on Wi-Fi Calling
  5. Choose a SIM card
  6. Enable or disable Wi-Fi Calling

Samsung Instructions