Verizon Wireless posted an announcement on their web site bragging that "HD Voice is now available on Prepaid." HD Voice is Verizon's marketing name for VoLTE or Voice over LTE. VoLTE promises clearer calls, and more importantly, the ability to use voice and data simultaneously, which is not possible without VoLTE using current Verizon LTE phones.
However, prepaid customers who tried were unable to activate the HD Voice feature yesterday. Users who called Verizon customer support were told that nothing had changed and VoLTE was still only available to postpaid customers.
About eight hours after the prepaid VoLTE announcement was posted, it disappeared from Verizon's site. Of course, things posted on the web never really disappear. You can still see the page announcing Prepaid VoLTE in the Google Cache.
At this time, Verizon VoLTE only works between two Verizon VoLTE phones. All the major US carriers including Verizon are working on enabling interoperability across carriers and between VoLTE and non-VoLTE phones, but full interoperability is probably a year or two away.
Verizon has announced that it wants to shut down 2G service by the end of 2019. Currently all non-VoLTE voice traffic on Verizon uses 2G as Verizon's EVDO 3G protocol is data only. That means that Verizon needs to insure that their VoLTE is filly interoperable and every postpaid, prepaid and MVNO customer has a VoLTE capable phone and VoLTE service by then. That seems like a tall order considering that it's taking them weeks, maybe months to flip the switch that grants prepaid customers access to a feature that their network already supports.
If you are curious which current Verizon phones support VoLTE, see this Verizon postpaid phone purchase page which is filtered to show only HD Voice capable phones.