ATT Nighthawk LTE Mobile Hotspot Router LTE Bands

Shoot, lost my first response.

Unfortunately, no.  There's nothing in the Mobile App or web based interface to choose a particular band.  Many have been asking for a similar feature.  Though in general most mobile MFG seem reluctant to give this capability.

I assume both bands are on the same tower?  If they were not, some have had success using a directional antenna tuned for Band 2 and pointing it at the tower with Band 2 (UL1850 - 1910  DL1930 - 1990 MHz).  You could also try a 700MHz filter.

Or an amplifier that lets you tune the gain on individual bands -- like this one:

https://www.surecall.com/signal-booster/home-office/FUSION4HOME/

Theoretically, once carrier aggregation is ubiquitious this should be less of an issue.  But, I've not yet been convinced my MR1100 is even doing CA on AT&T yet.  I agree, I often get faster download speeds on my old iPhone 6s.

Ultimately the tower  / band selection algorithms are controlled by the carrier.  They may just want to park on you on a particular band and will bias the device to connect in that order.  This is done on the carrier update file and/or by the tower.

-Jonathan