If you bought a second-hand B312E or switched carriers, this pop-up appears because the phone is "subsidized" to one network. The manufacturer (Samsung) and carrier don’t want you switching to a cheaper competitor without paying a fee.
Entering common defaults like 0000 , 00000000 , or 12345678 will almost always result in a "Wrong Password" error. If you attempt this too many times, the phone may permanently lock the security layers, rendering it unusable with any SIM card. samsung sm-b312e sim lock password