I have a Galaxy S2 which is SIM locked to the '3' network in the UK. I have contacted the carrier and they have provided me with an unlock code. However, when I am prompted to insert the code when I put in a different SIM card the code is rejected. I've also tried running the GalaxySimUnlock app which also came up with the same code that I got from my carrier.
My phone was originally updated to stock ICS but I then flashed it to CM 9 and then MIUI. I initially tried the sim unlock with MIUI running. I've now returned the phone to the stock 3 image - it's currently running 4.1.2 baseband I9100NELS1.
Has anyone had this problem before or can you shed some light on what is going wrong - I thought if I contacted the carrier this would be simple!