Readings & Meanings:
Sir, telephone for you.
Luxury items are taxed.
The radical is 言, words.
The phonetic element is 果, result (and fruit). We just looked at 果 here: http://sokasoka.blogspot.com/2008/04/fruit-has-come-to-fruition.html.
The connection is that you have to investigate (using words) in order to obtain results. This is such a task that you have to assign a whole "department" to do the investigation.
Bonus: Japanese Business Hierarchy of Titles
I translated 課長 as "sir." This is not accurate. 課長 means "section chief" or "section manager." But nobody says "Section chief, telephone," in English. The idea is silly to us.
But in Japan, that's how it goes. You call people by their titles. Additionally, there are several levels of power that you should be familiar with.
副社長 - company vice president
支店長 - branch manager
部長 - division manager
課長 - section manager
Did you think that was it? Ha! Far from it. I found a nine-pages-long PDF of almost all the titles in existence. It's here: http://www.j-net.org.uk/Miscellaneous/J-E%20Job%20Titles.pdf. I couldn't get it to open, though. I would suggest right-clicking on that link and downloading it as a PDF, or (more safely), you could go to the google cache of the PDF: here.