MBN file is a package for dedicate operator ,like AT&T , verizon , and common etc,
Nomally , module will select the right MBN file automatically , if you can register network normally , you do not need to care about it .
To disable MBN file , you can use the below AT cmd
AT+QMBNCFG=“Autosel”,0
AT+QMBNCFG=“Deactivate”