Really?

This is the sign posted on our PHARMACY DOOR. Since I started working about a year ago, I keep on asking myself if I am the only one who could see it or is it just invincible or unnoticeable. Even before I was hired I already saw this sign but then this very same sign is not that attractive enough for some people.
I am really pissed off because of this, because it happened not only once but a lot of times, and not just because the door is unlocked you can barged in directly inside. This sign is left unnoticed and these particular people just keep on going in and out of our territory.
I am a private person and even if the insides of the pharmacy is not my own sanctuary, I respect all of the things,people and anything inside. The simple sign is very much obvious for the unauthorized personnel not to enter. So, I'm really wondering if this sign is too hard to read or if is it too hard to follow!