I recently acquired a Sonya Ericson C903 handset, which was locked to the now defunct Three network (formerly Hutchison Australia) which was recently acquired by Vodafone.
Vodafone has a free service that provides the relevant unlocking code when given the IMEI number of the phone;
They will also provide the unlocking procedure as per the following document;
Now the problem is you need a working 3 network SIM, where do you get this from?
For free, you can go into any Vodafone store and ask for a ‘blank 3 SIM’, which you can use to allow you to follow the above Unlocking Procedure in store.
It is that easy.
Thanks to Vodafone for their free support helping unlock my phone.