Not a clue, what to do

A

AC Question

Hi,

I've got a galaxy S4, it got the KitKat 4.4.2 update which broke it!
I now get no service on the lock screen even though I can make and receive calls and texts. I also get Insert SIM card when I try to enable mobile data. I've narrowed it down to the sharecast dongle firmware update, before that installs its fine, after and it's broken.
It's been to EE 3 times and Samsung another 2 - coming back with the same issues every time. Yesterday EE swapped it for another phone which also has exactly the same issues.
EE now say there is nothing they can do and Samsung just hang up on me or tell me I need to call the repairs department who never answer the phone and never return calls after leaving a voicemail.
I'm only 10 months into my contract and have been without a working handset for 3 months!
What can I do - please help :(