Caller ID displayed number as (02) 9569 2907. Did not recognise number and figured if the call was important enough the caller would leave a message. Caller hung up as message machine clicks on. Within six minutes of this call multiple calls from "Private Number". Suspect overseas call centre is routing calls through an Australian Landline to see if anyone is home, signals telemarketers and then calls from individual telemarketers. Have had this happen previously with one caller admitting that this is sometimes what happens.