When connected to Wi-Fi, the notification screen may display "Internet Call" or "Wi-Fi calling" When not connected to Wi-Fi, the phone will use the mobile carrier If your Wi-Fi connection drops, your calls may switch to cellular networks Your existing call and text charges will apply when using Wi-Fi calling
When you're in a place with poor cellular service but good Wi-Fi or when you're traveling abroad and want to avoid unexpected charges.
If the Wi-Fi calling option is not available, it may be because the carrier does not support this feature. In this case, users can use a voiceover IP service such as Skype.