Hi I am new to this forum I have a GT-I9100 It was on Gingerbread I upgraded using ODIN, but the first time I tried it hung, so I restarted, Second time was successful. I am now on JellyBean 4.1.2 However, I did not backup phone settings (it was not in my idiots guide), qnd since I upgraded my phone cannot connect to the mobile phone network. The SIM seems fine as I moved it to an old Nokia 6310 and that allows me to make calls/texts but the Samsung is asking me for a Network SIM Unlock code. I am with Vodafone in the UK. I rang them, quoted my IMEI number and they told me that they could not find that number on their system. The IMEI number I quoted them came from an App, but when I checked the sticker under the battery, it is the same. As the phone was issued by Vodafone UK and I have been sing it for a year I am now very confused. I cannot register on the network, I cannot add an APN manually. I have now rooted the phone using PhilZ and still no joy. Has anyone esle experienced this problem, and if so, how did they fix it?