Secured Call works on both Wi-Fi connection and directly through your mobile carrier connection when no Wi-Fi is available.
We recommend using a Wi-Fi connection whenever possible to place or receive Secured Calls. This will provide optimal call performance and reduce (or eliminate) individual plan data usage.
If no Wi-Fi connection is available, you may still use Secured Call, however, performance may be less than optimal if you do not have a strong carrier connection. You may see a pop up message indicating that a lower performance connection.