After I upgraded to iOS 6 intinally I had wi-fi problems but it was connecting to 3g. So I reset the network settings and then it was connecting to wi-fi no issues. But when I tried connecting to 3g it is showing could activate celluar data. I tried the same sim card in my iPhone4 then it was working. I am not able to understand the problem. I tried reset network settings, removed the sim card, on-off power, pressed the home button and power button together but no improvement.