If it's truly, legitimately unlocked, it doesn't matter what carrier you decide to use. If it's unlocked, that means it's not "with" any carrier in particular.
If it IS carrier locked, then your first course of action should be to return it and get a refund as it was misrepresented.
Barring that, you can call AppleCare and give them the serial number. They can tell you if it's locked and to what carrier.
Yeah which is what i was thinking, but my only concern is going and buying a sim card for a carrier and it turning out to be locled to a specific provider. & i tried calling the person i bought it from to refund it but i haven't got much luck so far. I wasn't sure about if there was a way to call apple or not didn't think of looking into it much. thank you for the suggestion.