Why i cannot select network operator

I have a phone samsung A7 my sim were working fine til today.it says mobile network not available although the sim is recognised on.my phone.i have gone to mobile network and search automatically.it says connection failed try later I have also restore factoring still no connection 1 null on the icon on the sim. In another phone the sim works.please help me

from Android Forums at AndroidCentral.com - Ask a Question http://bit.ly/2Q3Lc1r
via IFTTT