Australia Reverse Phone Lookup

Unsolicited callers. Unfortunately my office number (not a main company switch number) is listed in the phone book. These people think i am residential - even when i tell them they've called through to an office. Harrassing calls from this number and the likes 'collecting data' on income etc. They will not disclose who they are collecting information for when asked. At other times they've called to try to sell services (primarily financial) - again without disclosing whom they are selling for. Sound like telemarketers out of Bangalore. Annoyingly persistent and hard to get off the phone without having to resort to being rude. There are other similar services but this one i've noted several times.