Samsung Eternity

Hello, i have purchased a samsung eternity , and i forgotten the passcode for the phone, now when i power the phone it asks for the passcode and i have no idea what it. and i called at&t and even the phone company, they gave me passcodes but nun worked. so i was wondering if it was a HARD RESET that i could do myself by pressing any buttons? its a 4-8 digit passcode . can someone please help me?