What specifically is the phone asking for? There are several different possibilities.
The phone password for this phone is user defined and has no default. If the phone is asking for this (for this model, it will show "Phone lock" at the top and "Password" just above the entry field), then it is a code that you have entered at some point. For assistance with unlocking a password locked phone, contact the manufacturer (in this case, 1-800-SAMSUNG).
There's also a PIN associated with the SIM card. If the phone needs that, most models ask for the SIM PIN or the PIN Code. The PIN can be changed but defaults to 1111.
If the SIM PIN is entered too many times, the phone will request a PUK code. That can be obtained through your myWireless account or by calling Customer Care.
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