i have android 6 software in my phone,recently I was update my phone in android 7, before update android6 my phone 4g network voice call also going, but now after update phone in android7 ,4g voice call not going without data connection, volte simple not come in display in android7, what can I do fo...

Hi, i am sulthan. I use bv6000 mobile , I have 4g network sim, if internet connection is off voice call not going, internet on then only going, what can I do, give me solition, android 6 call going now I update android 7 call not going,