And it's incredible how many human callers open with, "Hi, is this ____?" If you're contacting someone for a legitimate reason, don't do that. It's rude. First, identify yourself (and your organization if applicable), then ask for their identity. "Hi, this is Jennifer with First National Bank. Is this ____?"
My stock response for folks that don't do this: "Sorry, I don't identify myself to unknown callers. Who are you?" (It's okay to be blunt when they start off on the wrong foot.)