We don’t block capable devices, the problem is that not all VoLTE configurations work. Without testing device we can’t know if it will work with our network and usually brands with biggest market share send their prototypes and try to fix what is possible from their side and we from our side.
From my experience working for mobile carrier (not USA), I would recommend to contact your carrier to know if they support VoLTE for all capable devices or only for specific brands.
We don’t block capable devices, the problem is that not all VoLTE configurations work. Without testing device we can’t know if it will work with our network and usually brands with biggest market share send their prototypes and try to fix what is possible from their side and we from our side.