i get sony ericsson w700i from india.do i have to unlock in usa?

i must have to unlock this cell phone or i can use any prepaid wireless service.
in usa like att cingular
if its really locked phone can i use any function on the phone
only i can use a music player in this phone.
i don't know what locked phone look like.

There will be no difference in the physical appearance of a locked phone.Many network providers lock phones to their network and sell them at low cost. When users buy such phones they need to stay with that network till the contract ends. In this way the network provider increases their potential. Incase a user needs to unlock their phone in the middle of contract they can request their respective network provider. If they deny there are many online unlocking vendors like Superunlockcodes.com who provide permanent unlock through their unlocking service.You can check whether your Sony ericsson W700i is locked or not by inserting other networks with the phone.If it accepts the simcards then the phone is unlocked one...usually Indian phones are not locked as far as I know...