Hi Expert, I am using iphone 3GS with 3.1.3(7E18) version, its model is MC131B. I would like to upgrade it to allowable version of IOS. Please note my phone is jailbroken. Could you please tell me if I can upgrade to any newer version if yes then which version should i go for? And how can I do that? I have heard to upgrade IOS 3.1 to newer version, it puts up some problem with the phone. Appreciate your reply.