Unable to active my iPhone 6S activation server cannot be reached

Hi everyone,

I have iPhone 6S and after restarting my phone I am unable to activate it. Now it is giving me following error

Your iPhone could not be activated because they activation server cannot be reached. Try connecting your iPhone to a Mac or to a PC with ITunes to activate it, or try again in a couple of minutes.

I have restarted it multiple time, connected with iTune but no luck.

Thanks and Regards,

/Rizwan