I hv a iPhone 4S, and since i updated my IOS to 6.1.3, my phone gives me many problem such as sms halfway hang hang in dropbox my bluetooth goes off and cant restart my wifi cannot work my hotspot works occasionally   too much headache, how to switch my IOS back to 6.1.1 ???? I tried to use the restore button in iTunes to factory settings, but it is still at 6.1.3   Anyone can help???