Hi you can easily use your sony ericsson t280i mobile in usa ,but first you must unlock your mobile. You can easily unlock your sony ericsson t280i mobile by using unlock code. If you need unlock code you can visit this site Onlinegsmunlock.com here you can get the code and unlock your mobile. To get the code you have to mentioned which country is locked now,network provider and imei number. Then they send unlock code through email.After unlock your mobile you can use it with usa network and any other network.