Half a decade ago Verizon Wireless' network ran almost completely on a 3G technology called CDMA. While this particular technology had its strengths it had plenty of weaknesses, the worst of which was likely not being able to both talk and use data at the same time. This became a big problem as smartphones rose in popularity, with commercials from competitors highlighting the fact that their GSM networks could do both data and voice at the same time. Then there was the problem of speed, in which CDMA was not exactly the cream of the crop either. For these reasons and plenty more Verizon was the first big US carrier to push 4G LTE connectivity, and since then they've led the industry in nearly every single LTE-related category there is.
Last September Verizon unleashed Voice over LTE (VoLTE), a method of transporting voice communication via LTE data instead of the traditional CDMA method that has been used since the dawn of time. This method also allows for HD Voice, a significant bump in quality that makes the person on the other end sound like they're actually next to you rather than talking through a device. The LG G2 was the first Advanced Calling device, as Verizon calls it, and since then 16 total devices have been launched on the network. Since VoLTE was launched Verizon customers have made over 1 billion calls using the service, resulting in over 3 billion minutes of talk time for the superior voice service.
Verizon isn't specifying exactly how many of its customers are using Advanced Calling supported devices but it says that there are tens of millions of them out there. That's got to equate for a pretty significant percentage of its 100 million or so customers around the country. The latest devices added to the Advanced Calling supported list are none other than the HTC One M9 and the Samsung Galaxy S6 and Galaxy S6 Edge among plenty of others. Essentially it seems that if you've purchased a flagship device in the past year or two you're likely on the list of possible VoLTE Advanced Calling customers, and you'll most certainly know when you make that call to someone and they sound like they're standing right next to you.