I'm getting a daily call from a variety of area code 02-numbers, with no voice message.  

Hello - I keep getting these too.  Sooo annoying.  I block the number and then they call with another variation of the number.  When i call it back it goes nowhere.  Spammers are sooooooo disgusting : (

Same here, I tried to call the number back ( (02) 5924 5203 ) but I just get an engaged signal. My wife said she answered a call last week from an 02 number and it was someone from Telstra trying to get us to 'upgrade' our telephone plan. She handballs all that stuff onto me hence why they are still ringing !!