Constant phone calls from this number but they hang up when I answer. What is the point of that?

finally just got somebody to actually speak to me ...... after weeks and weeks of 4 to 5 calls a day ..
told me she was from craftmatic automatic beds and is doing a sales presentation blah blah ...that is as far as i let her get before giving both barrels ...they won't want to be ringing again

calls started arouynd July 2012. operation uses soft phone tech and out bound diallers.

calls from
(02) 8415 8516, or (02) 8415 8553, or (02) 8415 8580, or (02) 8415 8544, or (02) 8415 8503,
(02) 8415 8540, or (02) 8415 8587, or (02) 8415 8562, or (02) 8514 8594, or (02) 8514 8593, or
(02) 8415 8573, or (02) 8415 8593

if you dont answer within 3 rings call ends. if you do answer, person on other end will not say where
they are calling from ... and they after not selling you anything... then they want to know about your
employment status homeownership and income and savings etc

on three occasions, last on 10 October 2012, i told the caller I do not want to conduct any manner of business with him and his "organization" but the calls still come, about 4 or 5 a day.