My suggestions are as follows:
a) What are the office hours?
b) Why do visitors come to your office? How many visits occur per day? Have you analyzed their visits? Can you create a separate help desk for the subjects that generate the most queries?
c) What can you do to prevent their visits? Can you proactively provide information through your website? Are visitors required to obtain a form, fill it out, and submit it in person? If yes, can all of this be done through the website?
d) Can you be proactive in providing information through email, SMS, etc.?
e) Can you establish visiting hours for the visitors?
Thanks,
Dinesh Divekar