I'm sorry, am I your assistant?

The head of our department could technically be considered my "boss boss," but we don't work together often and I don't report to her.

Also keep in mind that there are two sales assistants that work here, whose responsibilities include what I'm about to mention below.

I get to work this morning and find an email from the "boss boss" stating the following:

Can you pls. post this online and also replace the sheets in the conference room with this one?

She emailed both assistants and myself. I'm sorry, but when did I become an assistant? There are two already, and this is NOT in my job description!!!