I was using Lumia Black and updated it to 8.1 ( Cyan) from my phone itself ( official release). I updated to Cyan OS not longer than a month back. Everything was fine, until recently, when i am going to connect call a "Flight mode". The flight mode will rapidly switch on and off. So, I am unable to use my Sim and thus, no whatsapp, no calls..social life has been paralyzed.