Band locking

New to the forum here. I have a question for the T-Mobile engineers, when will we be allowed to through a firmware update to lock the bands? My trashcan keeps switching back to primary B71(LTE) and no secondary connection. If I reset it I get primary band 2(LTE) and secondary n71(5G) AND MY SPEED DOUBLES through carrier aggregation band combination. I understands what the software is doing. The primary B71 has a stronger signal than the primary Band 2 but we need a choice. So please fix this T-Mobile engineers.