Madeline Sweeney calls
Flight attendants Betty Ong and Madeline Sweeney made (between them) several calls reporting the hijacking on Flight 11. The 9/11 Commission described events here.
Michael Woodward made notes of his conversation with Sweeney, and these were subsequently released amongst other 9/11 Commission documents.
Each call appears in the airfone phone records for Flight 11. These are the three connected calls (the second is split across two pages so we've pasted it back into one).