I think after 7 months the only thing any electronics company does is repair it (or replace for the same thing) The only way to get a whole different model is to call up 3 and threaten to leave because the phone was bad and no one will help out or whatever, chances are they will do anything to keep you. But I really doubt theyll just give you a refund after 7 months. I have heard so many problems through 3, even with decent Nokia phones that have no issues on any other network. Must be something to do with the software and fiddling around with them they do and it is just incompatible with every phone out there.
Def get the V3X on a $20 plan with Telstra if you have to get a V3X, they are the cheapest. Some places wont even stock them any more due to issues and Telstra are basically giving them away just to get them moving!