Source: iOS 7.0.2 Jailbreak iPhone 5
You can fix the iOS 7 activation error now. If you want fix this problem - you need to update your iOS 7 Beta 6 device to last iOS 7 Version (Today is iOS 7.0.2). How?
Method 2. (Recommended)
0) Download iTunes 11.1 (Google forever!!!)
1) Download iOS 7 firmware for iPhone/iPad/iPod Touch from the this links –> iOS 7 Download.
2) Open iTunes and connect your iDevice via USB cable
3) Select your device from the left navigation panel on iTunes 11
4) Hold down the Shift (Windows) or Alt/Option (Mac) key and hit the restore button on iTunes
5) Browse and select the downloaded iOS 7 IPSW file. Let the restore process complete.
Let us know how it goes leave a comment on us Facebook, Twitter or GooglePlus pages if you’ve any issues.