Brand new iphone works on unoffical carrier ? Last week i buy iphone4 8gb and before they start my offical carrier sim i but my own sim which is in roaming from another country n its working i got messages on it by another country carrier but when they start my phone by offical carrier it showing no sim . Can new brand phone can use in any carrier before u start any offical carrier?

I'm sorry but I don't understand what you mean

You have to specifically buy a factory unlocked phone if you want it to work on any carrier out of the box. By default many countries and phones are locked to official carriers if not specified as unlocked. Sounds like yours is locked.

Maybe what he says is that before let's say at&t activates his phone can he use a different sim. Well as BT said if it's offically unlocked it cost you around 800 bucks and you are able to use it with any carrier you want.

A phone company can always remove the sim lock after your flatrate expires.

Ya i am living in japan n here phone r factory locked but before they activate my phone i try to use it With another carrier n it can use but after activate cannot, is it every where like that?

Just try it.

Yes it's like that everywhere.