I've been doing my research on this very matter because I'm looking to change providers once my contract (with Telstra) is up in October.
I guess it depends on what network works best for you, and your usage.
Optus network:
The Optus network might be an issue for you if you go to regional areas much, as your phone won't support the Optus regional 3G network (nor parts of Vodafone's network in the bush).
As stated in the last post, Amaysim's PAYG plan could work well for you. You could buy a data pack (even a 10GB one that lasts a year) and PAYG for your calls (or VoIP), or use their $19.90 Flexi plan that comes with 500MB of data. They also offer an unlimited plan with unlimited calls/SMS to Australian numbers and 4GB of data for $39.90/30 days. Unlike the other Optus resellers, they don't offer 4G, 3G only (but with an iPhone 3GS it won't matter anyway).
Another which could be suitable is Yatango. I guess it seems rather like Ting in how it works with variable plans (but if you exceed limits you're charged at PAYG rates). Not quite as good value as it was (although now it offers 4G).
A third option is Vaya. They offer a range of plans, and their $18 one seems excellent value (with $650 of calls, unlimited SMS and 1.5GB data), and is 4G capable. IIRC it's postpaid though, not prepaid.
Telstra network:
Most Telstra resellers use part of the Telstra 3G network (basically slightly less coverage and possibly lower speeds compared to normal Telstra). Boost is an exception (it uses the full Telstra 3G network). No 4G, Telstra saves that for the mothership.
One choice is Aldi Mobile. They offer a PAYG plan for light users, but you'd need to sign up to one of the value packs or data packs if you don't want to pay by the megabyte for data.
There's also Telechoice, who offer a range of plans. Their rates seem to be lower if you sign up for two years.
It seems that Lycamobile have a deal which is unlimited calls and SMS and 2GB data for just $29.90 for 30 days. I'm sure they have other plans as well for lower usage.
One which I recommended to my brother (he seems happy with it) is Boost. $40 for 30 days, unlimited Australian calls/SMS and 2GB data. Unlike the other Telstra resellers above, it's actually using the full Telstra 3G network, with its 99.3% population coverage.
Vodafone network:
There's fewer Vodafone resellers that I can see, but there's a few around, and from my experience, the Vodafone network has progressed a long way since the days of Vodafail.
Lebara have a deal similar to the above Lycamobile one (unlimited calls/SMS/2GB for $29.90). They seem to offer PAYG prepaid as well.
Another Vodafone reseller would be Hello Mobile, which have a $39.90 prepaid plan with unlimited calls/SMS/4GB for 30 days (along with a few other plans).
Some others I've seen are Think Mobile, Kiss Mobile, CMobile and Reward Mobile.
Can you tell I'm looking forward to no longer giving Telstra $107 a month? :)
I've looked into early termination, but it's cheaper to just see out the remaining five months of the contract than pay the early termination charge and another carrier for that time.
BTW, YMMV with these carriers, not being held responsible if they do a Kogan and abruptly shut down. :)
