they do reply though but you will not be satisfied with their answers most of the time. When they saw your subject that you replied back they're not gonna mind it so maybe they will skip your email. So its better to make new mail everytime.
Let me know Chu if they reply. I'm praying for you that they will reschedule your date of interview at the earliest possible. Don't stop believing! I was once in your shoe.
. NVC also mailed to USEM Abu Dhabi for my expiated process they didn't reply. 
