BaseBox 5 + 4G LTE miniPCI Express D15G2 band problem

HI all,
I have a problem. My modem switch band from 1800 to 800 sometimes what is a problem, becouse signal strenght change to worse. When I try force to use band 1800 on Miktotik I get:
[admin@R1] > /interface lte set lte1 band=“3”
input does not match any value of band

Please help me.
lte2.JPG
lte3.JPG