Okay well, VZW just doesn't wanna play nice with U1 devices no matter what way you try. The U Firmware loads all the typical VZW bloat etc., and you can access WiFi calling/VoLTE. However, the native Video Calling isn't accessible, and the chat features are not working. You can't even access their settings, so the best flash over from a U1 is to TMO in my experience so far. TMO grants full access to all features, and assuming AT&T is probably similar. However, one odd thing with TMO that's been persistent for a while now, is the refusal to play nice with the native Visual Voicemail app. Strangely VZW doesn't mind if you use the native VV app over VZW's, but for some inexplicable reason TMO only gives you the option to call in when you attempt to use it. I much prefer Samsung's implementation of VV over TMO's so that tidbit is annoying. If anyone knows a workaround for that, I'd appreciate the fix.