Made my first HD call today and was actually confused/surprised. Most of our area has VoLTE but not many people I call have a compatible phone. I've browsed the net while on a call (Verizon) with my wife on her 5S but never actually used the calling side of it. Called a friend today with an iPhone 6 and instantly realized we were on an HD call. He didn't even realize it at first until I pointed it out. But wow, what a difference it makes. Good to see the future is finally free of muffled, tinny phone calls.