The biggest problem here is...
The sods keep turning off network generations. First 2G - had nice small, light, long battery life phone for years until they pulled the plug on 2G. In a few weeks the 3G network will be gone and my Asha 300 is then ewaste.
I think the EU retained 2G and retired 3G when adopting 4G/LTE?
I guess used/refurbished phones in AU aren't going to be too old because of this.
My main gripe is that recent smart phones are mostly large >6 inches (>150mm) and heavy.
The samsung galaxy core prime at 4.5" (115mm) was about the right size for the shirt pocket - not that shirts seem to come with pockets these days (I suppose I should be grateful they still button up on the same side. :)
In these parts once you omit the flagships products and anything apple and most samsung the remaining brands have a much smaller market share and are priced very competitively - especially the older models.
Prepaid offerings from the major providers (telstra, optus, voda) are/were often at fair discount but are/were locked to the provider's network but if you were already using that provider anyway the phone would work with your existing sim.
I found the cheaper nokias are not too shabby at all, and a cheap 3G huawei was as good as a more expensive samsung. For lightness I use a smaller opel very very cheap, nasty perhaps not too nasty but can't keep the time(?) and loses the plot if VoLTE isn't enabled. Not the middle kingdom's proudest export I suspect.
Anyway not many people would want to call me. ;)