Is there a way I can force 3G instead of LTE on Netgear LB 1120?

I've been doing some testing in my area, and even with a cell booster and full bars (-56 db) on Walmart Family Mobile (T-Mobile) LTE band 12, I can only get a maximum of about 4Mbps down and 1.5 Mbps upload...  sometimes dropping below 1 Mbps. The few times I tested without the booster and only used the internal antenna, it would sometimes drop to 3G. When dropping to half bars of 3G (-95 db), I'm able to pull 8 Mbps down and 3 Mbps up. So the question.. Is there any way to force this device to only use certain bands? And any tips as to why the LTE may be working so poorly? I am in a rural area, so I wouldnt think the towers would be too busy, and I do get a small amount of signal even without the booster.