OMG so I checked the FAQ for my supplier (Aldi mobile):

Can I use WiFi Calling when I’m overseas?

As long as you’re connected to a compatible WiFi network overseas, you will be able to make and receive voice calls at your standard rate; as if you were still in Australia.

I can’t believe it. All this time, I could have been doing that! Ha ha! Thank you!

Google meet

Thank you. I’ve been looking, but can find no info on whether or not the ID I call from is an Australian number or not. Without that, my customers just won’t pick up the phone, so would be pointless. I will try and research this further as an option. Thanks again.