NatebirdNot sure what band 71 has to do with any of this. This phone has never had and 71 and T-Mobile still uses their other bands (like 2, 4, 5, 12). Sure that might limit it in some areas but it has nothing to do with lack of support. That is a hardware limitation that can't be changed and has been that way all along. voLTE works fine on T-Mobile now (and could be updated to work for cricket and ATT). And it's support seems to have fixed the missed texts and calls that were not uncommon prior to voLTE.
See not compatible anymore until VOLTE is added support from Asus with ATT Cricket Wireless T-mobile has no support for band 71 which means cellular support for Asus phone's on Tmobile is horrible so that leaves ATT and Cricket Wireless or other mnvo carriers that used UMTS/HSDPA won't work anymore until support is added with a firmware update for Zenfone 6 VOLTE support on Cricket Wireless and ATT until then phones don't work anymore