So this is my second iPhone 6s Plus where VoLTE isn't working. I have LTE on for voice and data latest 9.3 update and carrier update 24.1 and yet when I make phone calls it drops to 3G. I been told you can't have wifi calling on and be able to do VoLTE I been told my phone is defective but 2 iPhones in a row being defective? Doubt it so i dont know what to do