Hi, My Dad might switch carriers and his new carrier has offered him a free iPhone 3GS. He says that he is willing to exchange his iPhone for my Blackberry. I am tied to my company's plan (from another carrier) so I would have to unlock the iphone to use it with my SIM. How simple it is to unlock an iphone to use it with a different carrier? Should I upgrade it to IOS 4 first? Do I have to jailbreak the phone first in order to unlock it? And can I un-jailbreak my phone later and leave it unlocked to be able to install updates?