When Wi-Fi calling is on, your device can make and receive calls via Wi-Fi networks. Your device will choose to make calls via Wi-Fi or over a cellular network based on which signal is stronger at the time.
Note: Wi-Fi Calling allows you to make and receive calls over a Wi-Fi network if cellular is not available.
From the Home screen, tap Settings.
Scroll to Phone.
Tap Wi-Fi Calling.
Tap or slide the Wi-Fi Calling on This iPhone switch to ON.
Note: If necessary, follow onscreen instructions to enter an address for use in the event of an emergency call. You can update this address at any time.