HD Voice is an audio codec, that gives you crystal clear high definition voice calling without background noise. It’s like talking to someone in the same room, even if the Vodafone Warriors have just scored.
You won't need to switch HD Voice on. If your phone supports HD Voice, it's enabled by default.
Vodafone launched HD Voice in February, 2013, to work with 3G calling. HD Voice is also known as Wideband audio.
VoLTE also provides clear calling, delivered over 4G. VoLTE needs to be enabled in the settings on your phone.