From a Home screen, tap the Phone icon (lower-left).
If unavailable, swipe up or down from the center of the display then tap Phone .
Tap the Menu icon (upper-right).
Tap the Wi-Fi calling switch to turn on or off .
If prompted, review the info then tap Turn off Wi-Fi Calling to confirm.
When activating Wi-Fi calling for the first time, refer to Activate Wi-Fi Calling - Samsung > Android 9.0 for additonal setup instructions.