You should have no problems upgrading to the latest iOS version, which is iOS 8.1.2. Unless you have a fast reliable internet connection you may want to download the update to iTunes on your computer then connect your iPhone to your computer to complete the upgrade process.I am from India and using a iphone 5 unlocked from AT&T . And now i want to know if i can update the ios 6 to ios 8 or later version of it..