How to lock to a specific LTE band with 6335-MX?


Can anyone tell me the process of locking LTE band. I want to lock B4 LTE band on 6335-MX because its keep changing with B12 .The reason of lock is that system at 30% catch B4 while at 55 % catch B 12 and also B4 is faster in speed.

I am using the Arduino Mega board for programming purposes.