knock knock

Today while leaving home, I had to go to the apartment of head of the hsg society, where I stay in a rented flat and give the society charges that my landlady had given me. I rang the bell, a voice called out from behind the closed door - "Who is it". Now, I have never talked to these people, and even if they have seen me around, how do they know my name. I said, fumbling a little, "Its me". The reply, as expected "who me?" I called out my name. Before they could say anything further, I said I wanted to give the society charges.

Ok, now why do people call out "who is it". Doesnt it occur to them that the person at the door might be a first time visitor. Ok I accept that, but now what should one reply when faced with this question. Something like the knock knock jokes like the one below.

Knock Knock
Whos there?
Boo
Boo Who?
Ok now, dont cry.