A master of the succinct reply I see
The guy at the Optus place was pretty sure they are unlocked these days, but in any case he said they can be unlocked totally free of charge these days. To find out how, just visit here ...
https://msc.optuszoo.com.au/iphone/unlock
A bit more information for interest sake is available here ...
http://iadrenalin.com.au/tips/unlock...vodafone-free/