One still can receive SMS on Digi WiFi Calling in airplane mode. Several SMS blasted in last time i was connected to the plane's WiFi somewhere over Europe. I guess it's up to how the mobile carrier configures their WiFi Calling/VoWiFi.

I’m overseas now and was surprised to see Maxis VoWiFi icon appearing on my secondary phone, a Redmi phone.

I initially saw the VoWiFi icon yesterday and instead of local telco’s name, MY MAXIS appeared instead. I then switched it to Airplane Mode, and VoWiFi icon is still connected along with MY MAXIS appearing next to it.

Just now I decided to try to use it to call my own Digi number. iPhone is able to detect that the call is from overseas by showing the country’s name. I then connected to a Malaysia VPN and iPhone is still showing the name of the country I’m current in now.

Anyway, I checked my Maxis unbilled charges via the Maxis App and there is none. But to be 100% sure I need to wait till the next bill is out.