Was on Spotify. They run on Optus 3G.
Rates appear to be a bit dearer than amaysim, but if you're just after the $10 sim for one month then I guess this is for you.
Edit: they're kinda like UK's giffgaff mvno, earn credit with referrals and on forums.
is this one of those offers where you provide your CC details and after 30 days if you forget to cancel then you are automatically put onto on of their monthly plans?