You can turn Wi-Fi Calling on or off in your phone's settings. With Wi-Fi Calling, you can call, text, and use Visual Voicemail as you do on the cellular network. While in the U.S., Wi-Fi Calling can be used when a cellular signal is weak or unavailable. While traveling in many countries outside the U.S., your phone will automatically use the Wi-Fi network instead of a mobile network when both are available. (Wi-Fi Calling is restricted in some countries.)