Funny Phone Call

Today I spent the whole day at home. I received about 8 phone calls on my home phone. 7 of them were sales. One of the 7 was a lady who said,

"Hi, is John there?"
Me: "There's nobody here by that name."
Lady: "Oh, you don't know him?"
Me: "Um, if there were someone named John that lived here I would hand him the phone."
Lady: "Ma'am, I was just asking if you knew him, not if he was standing next to you."
Me: "Uhhhhh" (I LITERALLY had no words for her).
Lady: "Thank you and have a nice day."

Ok, here we go:
So, how the heck am I suppose to know who "John" is???? John with no apparent last name. Because I know EVERY single John who walks the planet? If I knew of a John, especially if one lived in my house I would have said, "Sure, let me get him," or "he's not here right now, may I take a message?" Oh, dear sweet lady. There really are NO WORDS!