Zimmerman called the non-emergency Sanford police number and talked with a dispatcher. The media has used '911 operator' either because they're too dense to understand the difference, or because it was easier and like a shorthand reference to them, or both.
The City of Sanford made it clear back in mid-March that Zimmerman did not speak with 911, but a non-emergency dispatcher.
Angela Corey's charging affidavit is careful to make that distinction as well.
So it wasn’t even a 911 operator? It was just a person on the phone? For all GZ knew it was the janitor.