VoLTE: How to use it and why you should care | Android Central
https://www.androidcentral.com/volte
VoLTE — or Voice over LTE — is the new standard for calling throughout the U.S., Canada, and By now, VoLTE is most likely available in your area, and if you upgraded your phone in the last few years...
Voice over LTE - Wikipedia
https://en.wikipedia.org/wiki/Voice_over_LTE
Voice over Long-Term Evolution (VoLTE) is a high-speed wireless communication standard for mobile phones and data terminals, including Internet of things (IoT) devices and wearables. VoLTE has up to three times more voice and data capacity than older 3G UMTS and up to six times more than 2G GSM.