Ok guys, here is a temp fix for you to continue using the mobile hotspot. But I am not sure how long it will be able to work until it gets blocked.
Go to Settings
Mobile network
Access Point Names
New APN
set the name
set the APN to: epc.tmobile.com
save
after you save, select the new APN you created instead of T-Mobile data.
Go to Settings
Mobile network
Access Point Names
New APN
set the name
set the APN to: epc.tmobile.com
save
after you save, select the new APN you created instead of T-Mobile data.