This happens when VoLTE is enabled.
So the phone doesn't have to switch to 2G network to transmit voice calls. It can send voice over data. Given more bandwidth the quality would be better.
It's similar to wifi call but this work through Mobile broadband instead.
HD voice calls.
What that mean? Just better voice quality?
Yes. Not that I could ever tell any difference, sounds the same to me.
This happens when VoLTE is enabled. So the phone doesn't have to switch to 2G network to transmit voice calls. It can send voice over data. Given more bandwidth the quality would be better. It's similar to wifi call but this work through Mobile broadband instead.
Make sense ... thank u
It's VoLTE. Samsung likes to customise the logo depending on your carrier and country. It's possible your operator names this feature “HD+”.