Australian media regulator publishes a list of numbers used only for fictional purposes like TV shows or whatever:

https://www.acma.gov.au/phone-numbers-use-tv-shows-films-and-creative-works

I’ve always used the first one. Every store seems to have it registered a billion times. They sometimes say “woah there’s 100s of people on this number” and I just tell them to pick one. They never care.