I have the unlock code T-Mobile sent so our son can use his phone with
prepaid SIM cards when he's overseas on a study program.

Do we enter that code now to unlock the phone, or does he have to wait
until he has the "foreign" SIM card? Some Web sites seem to say that the
"foreign" SIM card has to be in place first. And if that is so, does it
unlock the phone only for that specific SIM card?

Perce