I buy my new phone about month ago,i had 4.3 JB firmware,and then i update to 4.4.2,then i seen a problem i can't call someone,i can't use mobile internet,i can't receive a messages or a calls,i tried to downgrade again to 4.3,same problem,i tried to insert other sim card,i tried everything and nothing works,my Wi-Fi works but not Sim-Card,It says "Not Registered on Network" :-