Netgear MR5200 100NAS

hello,

i purchase a MR5200 ( 100NAS version) from amazon to my country (Vietnam), the band n41 does not work,

my firmware verion is: NTGX55_12.04.10.01

web app version: MR5200-100EUS_04.02.196.00 

what should i do to unlock the n41 band?

please contact me via email anex3655@gmail.com

many tks,