Google Nexus 6P

despite the fact that nexus has stated that volte is possible.


Source
 
It's the restriction employed by the developers,they don't want to work on older SoCs,or might be a marketing strategy put on by Analysts,every LTE enabled modem supports VoLTE,just need a proper software layer to make it work..
 
Mine died with bootloop issues just in the 15th month. lost all my whatsapp and sms for those 15 months. No Warranty of course. OnePlus 3t is doing well for now.
 

Back