Samsung I9300 - Network unlock fails I recently flashed a custom ROM on my Samsung I9300. Everything is working fine, except I have to enter a 'SIM network unlock PIN'. I assume, that this is not the usual 4-digit PIN code. If I enter the correlating correct 4-digit PIN, it says 'SIM Network unlock request unsuccessful'.


I tried different SIMs from different providers which are working in a different mobile phone.
The problem appears with Slim 5.1.1 and 4.4.4, CM12.1 and OmniROM 5.1.


My phone was running stock firmware Android 4.3 and I never had this problem (even if I once changed my provider).
There are plenty of tutorials about how to unlock the I9300, but none worked so far, there are also many non-free services for unlocking which seems rather untrustworthy to me. It would be new to me, if the phone is or was ever branded.

There is the possibility to unlock the phone by using the service menu by entering the secret/hidden code 


##197328640##


like shown in this tutorial: https://www.youtube.com/watch?v=f1hzeBEeO_k.
Why is the code (or others) in Slim not working?

Could you please verify too that the only possibility to unlock the SIM is to buy a specific unlock code?
I got the phone unlocked at a local mobile phone dealer for € 20. This worked.

Generally I'd say it is interesting how this network SIM lock comes from, because my phone never has been locked or branded by a provider. The stock firmware worked with different providers. The problem only appeared for the custom ROMs.

And be aware when changing your SIM card! I broke mine 2-times only by exchanging it (probably scratching the chip's surface) and had to buy a new one and get the old number transferred to the new.