In Australia, unfortunately, all phones are sold in locked condition. It means we are bound by the carrier to use its service using its provided phone. This not uncommon in Australia but It quite surprised me when all phones in Indonesia (at least when I left) were all unlocked.
I had this experience when I bought a phone from Optus. They said that I can’t use my phone for any non-optus provider. I refunded it, just after they told me the condition.
Thinking to buy a new phone and unlocking it drive me to www.freeyourgsm.com and www.unlockme.co.uk. You might want to read the tutorial here.
However, I was quite surprised when I go to www.vodafone.com.au, one of the carrier in Australia, and I found this on its website.
This handset is locked to the Vodafone network. Vodafone will supply your unlock code free of charge.
I followed the link and, voila, Vodafone gives a free unlocking code for its phone.
I google-ed www.three.com.au and found that three also providing free unlocking. But I couldn’t actually find it on the web site.