HT201263 already done these steps but cannot activate :(

Question

my phone is iphone 3gs, i updated my ios to the latest version last night, after the long process, it wont activate. its been 18 hours after the update.
error in activating is
Your iphone could not be activated because the activation service is temporarily unavailable. Try connecting your iphone to itunes to activate it, or try again in a couple of minutes.
If the problem persists, contact Apple support.
~done contacting Apple support and followed activation process, still no change. Please help.

Answer 1

There are four primary causes of the activation error:
The activation server is unavailable. Rare, but it happens. Usually fixed within minutes.
Your antivirus or firewall (or your router's firewall) is blocking access to the domain gs.apple.com on ports 80 and 443.
Your phone is jailbroken, as Tim suggested may be the case.
Your phone isn't jailbroken, but the computer you are connected to during the restore or update was used to hack or jailbreak some other iOS device, and its network database was corrupted in the process.
Perhaps this will provide you some clues as to how to proceed. If your iPhone has not been jailbroken, Apple has some troubleshooting suggestions here:
http://support.apple.com/kb/TS3424?viewlocale=en_US 
If your iPhone has been jailbroken, you're on your own. We can provide no assistance for jailbroken devices in these forums.
Regards.
(part of the above information quoted with gratitude from Lawrence Finch)