My total annual mobile expenditure is $20-40 -  I do not need data packs or unlimited texts or "free" minutes. I want to have $20 credit available over 365 days to make calls or send text messages at standard rates if I need to in an emergency. My phone busted recently and I have to buy a new one, I have an old Vodafone SIM that is on Supa I think (I really didn't pay attention), I only know that with that one I can do as above for now. Unless I buy a phone that has a different sized SIM slot and have to get a new SIM, since Vodafone say they don't offer those Prepay plans anymore. I want to keep my options open for phones and even networks, so I'm trying to find out if I can still use my phone in the manner I always have if I switch providers or need a new Vodafone SIM.

Do Spark, Skinny, 2Degrees and Vodafone still work this way? As far as I can see with all of them you load credit, then purchase a 'plan' that expires after a month unless you buy the plan again.