My smartphone drops calls made using Wi-Fi calling
You can only make calls using Wi-Fi calling if your BlackBerry smartphone is connected to a Wi-Fi network. To avoid
dropped calls, your smartphone plays a warning tone when you are making a call using Wi-Fi calling and your Wi-Fi
connection is getting weak. To make another call using Wi-Fi calling, move to an area with a stronger Wi-Fi signal.
User Guide
Manage Connections
310