Here is a detailed explanation by one of the Oracle's Luddite. "SIM network PIN blocked. Enter SIM network PUK." is asking for the phone’s (often Samsung) “master code" after entering the wrong code too many times. Samsung and/or your previous carrier can give you this. "SIM network unlock PIN" is asking for your previous carrier's unlock code - just contact them with your IMEI and they'll give it to you. If you enter this incorrectly too many times, you'll get the error message above.
