That is what I had before retirement. I found that neither the texting nor the voicemail notification / visual voicemail was that reliable over Wifi calling. Sometimes when I enabled cellular, I would get notifications of voicemail left for me earlier.

Visual voicemail came way before Wifi Calling. I would think they would have enhanced and perfected the VMM technology by now and it would work over Wifi...

It seems this might be phone and carrier dependent? For example:

https://support.bell.ca/mobility/rat...article?step=7 - "Note: A data plan is required for iPhone Visual Voicemail to work. It is not available through Wi-Fi."
https://www.verizon.com/support/visual-voice-mail-faqs/ says IOS works over Wifi but not Android

???