Iphone 3gs ICCID Unknown?

I upgrade my iphone 3gs from ios 4.1 to ios 6.1.2 because when connect to itunes that the device is upgradable to ios 6.1.2 then installation of new ios the iphone cannot activated because the activation server is temporarily unavailable then Unknown ICCID? Everyone can help me how to restore the ICCID on my phone to activate?