apple ID sign in error

am operating IPhone 4S, ISO 9.3.4, every time am trying to sign in my apple ID it says "Verification failed There was an error connecting to the Apple ID server". i have done software update using Itunes and the process was successful, tried to rest all network settings, restarted the router several times, other applications like safari could connect to internet perfectly well.. but the problem still persist. PLEASE HELP ME