Who I have the same questioned this topic

Is there a way for the user to receive the VM over WiFi in case of no data/reception? Is that a feature I need to turn on?

Problem: While overseas I'll still use the phone but in airplane mode with WiFi antenna on. I can send/receive text over WiFi (Thank you Vz! This is awesome!) but cannot receive the VM.

If not, can Vz please consider permitting that feature just like texting? Thank you.