use iphone 5s in VietNam
I bought iPhone 5s in america and brought it to VietNam. I can't use it with Viettel SIM. when I insert SIM, it like this
please help me... thank you!!!!!!
iPhone 5s, iOS 9.1
one can buy a cheap phone if it's locked to a carrier for a period where the carrier make up for the part
of the real price of the phone that the carrier paid by your usage of their services
this is called sim lock you can read more
https://en.wikipedia.org/wiki/SIM_lock
when a phone is sim locked only the carrier it's locked to can unlock it
even if the phone manufacture wanted to doing so would give them a huuuuge law suit from the carriers
so take contact to the carrier in usa your phone is locked to and try getting them to unlock it
or sell the phone to somebody who will be using that carrier in usa anyway