can i know what the function of USB slot in D-Link DIR-615 and in the STB??

hey guy, i'm VIP20 user here, just install few day ago, but since yesterday i cannot access internet at all, never touch anything, but suddenly cannot access internet, and now LED in BTU unit only show for LAN1 and POWER, no LED for AUTH and LINK, what the possible cause of this? i already made report to unifi CS and they say technician will come, but till now no technician come, tried to call their CS to force their technician come early, but seem their CS always busy...

"Harap maaf semua pegawai perkhidmatan pelanggan kami masih sibuk" damn tried from 11am till now still sibuk...

TM technician has come and fixed my unifi problem, the problem is cable and the box outside my home..
my current speed



extra 9mb/s speed for the download?? but seem upload speed to be slow..