WiFi Calling clarification and problems

[capun1950]

I need a clarification about setting up WiFi calling, specially while overseas

1- Should Airplane Mode be turned on or off?

If I turn it off the WiFi Calling options are no longer available (Grayed out)

2- I follow the WiFi Calling FAQ and the part that I am not clear is in this section

"To change your preferred network on your Android device:
Go to Settings on your device.

Tap When Roaming and select the network you want to use while roaming:
Prefer Other Cellular Network (default)
Prefer Wi-Fi"

While overseas should it be set to WiFi instead of a Cell network?

3- Our son is in Europe and he turned Airplane Mode On and WiFi on and was able to get and send text messages in Barcelona.

But while in Venice he cannot get/receive text messages.

Is the problem a country/WiFi problem or he has to turn Airplane Mode Off (see question #1)

Thanks

Update

Seems to be a WiFi provider issue, he tried a different WiFi and it works 

[vzw_customer_support]

capun1950, keeping you connected with Wi-Fi calling when overseas is important. We are here to provide all the information that you need. Here is a web page https://www.verizonwireless.com/support/wifi-calling-faqs/ with the details to get you started. Wi-Fi calling allows you to make and receive calls to and from U.S. numbers free of charge while traveling internationally. Turning on Airplane Mode cuts off all cellular service, so having that feature on will be a good idea to prevent any carrier charges. You can still use Wi-Fi related services, such as Wi-Fi calling, but you will need to go back into settings, select Wi-Fi and reconnect to Wi-Fi after initially turning Airplane Mode on. We recommend selecting Prefer Wi-Fi while traveling internationally. Regrettably, it will be hard to say what happened on your son’s trip without more information. We can speculate that the Wi-Fi signal may have been weak or some settings may have been adjusted. You can also add a temporary international plan to provide cellular service for calls, text, and data when there is not a Wi-Fi signal nearby. Here is our international web page http://www.verizonwireless.com/international with all the options. Does this help?