I've asked a Comcast employee to help you. You should expect a reply in this thread.
M4ST3R, The LG X charge is VoLTE capable. Did you receive a ticket number for the Tier 2 work being done? If it isn't working on other devices, it sounds like a provisioning issue.
M4ST3R, I have heard of a VoLTE activation issue for this device before. Has tier 2 opened a ticket for your issue? If not, I can do so. Please let me know.
M4ST3R, some customers aren't able to enable that feature on some devices. Our Tier 2 and 3 teams are working on a fix.