How To Name Column From Data Stored In Certain Row

I am trying to name a column from data stored in a row (Phone number) I want to name it from the first 3 digits (Area code) and I have no clue how to do it I have Googled but I think the query is a little too complicated for me to explain it and get a result from Google or find it in a section of a book.

My phone numbers are strings, so I initially look for the first 3 characters and then start separating and counting, I can do that, the only problem I have is naming the column WITH the the first three digits that I just separated.

I am trying to learn by myself how to use databases and am using the HR database that comes in oracle since I read in a forum that it is a great way to learn how to use queries.

I read about using Pivot to do it, but in pivot I need to know how many area codes there are. I will post a screen shot of the table that I am working on the other post

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I can group by phone number with this:

SELECT SUBSTR(PHONE_NUMBER, 1, 3) AREA, COUNT(SUBSTR(PHONE_NUMBER, 1, 3)) TOTAL_COUNT
FROM EMPLOYEES
GROUP BY SUBSTR(PHONE_NUMBER, 1, 3);

But what I am interested in doing is that instead of Area appearing as a column, that the actual first 3 digits would appear as the column name.

This is kind of what I am trying to do, but instead of AREA appearing as column name I would like for each one of the area codes to appear as column name, here is the

SELECT DE.DEPARTMENT_NAME, EM.SEX, SUBSTR(EM.PHONE_NUMBER, 1, 3) AREA, COUNT(SUBSTR(EM.PHONE_NUMBER, 1, 3)) TOTAL_COUNT FROM EMPLOYEES EM, DEPARTMENTS DE WHERE DE.DEPARTMENT_ID = EM.DEPARTMENT_ID GROUP BY DEPARTMENT_NAME, EM.SEX, SUBSTR(PHONE_NUMBER, 1, 3) ORDER BY DEPARTMENT_NAME;