Greetings @tjabs and welcome.
The last update from devs is that VoLTE will be supported in v0.17. If you’re in the U.S., the Samsung S9 paired with AT&T via the RedPocket Mobile MVNO works most excellently without VoLTE - I know this first hand! 
There are others in the forum that have had success with T-Mobile as well. A search of the forum will reveal specifics of the different solutions employed.
There are many valid reasons why someone would not choose an /e/OS device- don’t let lack of VoLTE be the primary determinant! 
As you go through that process, let us know how you choose to proceed and good luck.