Thinking of switching to iOS mobile devices. One way my wife and I got burned buying devices running The Other OS was they were supposed to have Band 12 support, in fact they have the hardware, but, the manufacturer declined to add VoLTE, or go through T-Mobile's rigorous or expensive (?) qualification process, so: No Extended Range LTE for us 
Brand-spanking new iPhones are out of the question, for us. Not passing judgement on others' buying habits, but, they're too expensive for our budget. So I'm thinking maybe iPhone 6 or SE. But I'm seeing conflicting reports on support for Band 12 and VoLTE for these on T-Mobile.
This page: Ultrafast LTE. Available in more places than ever before, Apple's own, seems to present contradictory information.
When I originally looked up specs, this indicated no, for the iPhone 6: GSM Arena - Apple iPhone 6 - Full phone specifications
But, then I ran across: T-Mobile - Extended Range LTE - COMPATIBLE PHONES and Spectrum Gateway - Devices compatible with Extended Range LTE.
So the preponderance of information indicates we'd be good to go on T-Mobile's Band 12 and VoLTE. But, once burned, twice shy.
Can anybody here testify personally to having used an iPhone 6, 6s or SE on T-Mobile with VoLTE on Band 12?
Thanks!

Brand-spanking new iPhones are out of the question, for us. Not passing judgement on others' buying habits, but, they're too expensive for our budget. So I'm thinking maybe iPhone 6 or SE. But I'm seeing conflicting reports on support for Band 12 and VoLTE for these on T-Mobile.
This page: Ultrafast LTE. Available in more places than ever before, Apple's own, seems to present contradictory information.
When I originally looked up specs, this indicated no, for the iPhone 6: GSM Arena - Apple iPhone 6 - Full phone specifications
But, then I ran across: T-Mobile - Extended Range LTE - COMPATIBLE PHONES and Spectrum Gateway - Devices compatible with Extended Range LTE.
So the preponderance of information indicates we'd be good to go on T-Mobile's Band 12 and VoLTE. But, once burned, twice shy.
Can anybody here testify personally to having used an iPhone 6, 6s or SE on T-Mobile with VoLTE on Band 12?
Thanks!