I've got a Nokia 5190 with a Cingular SIM card now. Will I be able to put an AT&T SIM card in it? Are SIM cards sized to fit certain phones - or are they the same size in all phones? Also, how do I tell if my 5190 is provider locked - whereas it won't work with anything but a Cingular SIM card?
If the 5190 is unlocked you should be able to put the SIM in and restart the phone and you are all set!
If the phone says something to the effect that the SIM is not accepted...your 5190 is locked to Cingular. It might be able to be unlocked for a small amount of money but I don't know Cingular's unlocking policies.