A：Why aren't you at work?
你为什么没上班?
B：I called in sick.
我(打电话)请病假了。
注释：
a.be at work在上班/在工作
b.我们告诉对方自己打过电话到办公室请病假，所以没去上班时，理论上可以这么说：
I made a call to the office to say that I was sick and, therefore,I couldn't go to work.
实际上可以简短地说：
I called in sick.
(我请病假。)