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
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?