Phones in the Library

I've started spending time in the library during my lunch hour to do some reading and work on some personal research.  A few minutes ago I was disrupted by the sound of a cell phone ringing at top volume.  I heard the owner shuffling around to get to the phone.  I understand that sometimes people forget to silence their phones in the library so I figured that's what would happen next.  Instead, I heard a loud clear "hello?"  The owner of the phone proceeded to hold a conversation that I could not escape hearing anywhere on the third floor.  I ended up moving to the opposite side of the library near the ongoing construction project.  The hammering is actually less disruptive than the phone conversation that shouldn't be happening.  It always amazes me that people literate enough to use a library at a graduate school can't read the "NO CELL PHONES" sign at the entrance to every floor.