An Illawarra private detective says up to 10 people a week are approaching him after becoming victims of phone scams.
Overwatch Investigations director Stephen Patterson said there was no guarantee that victims would be able to recoup their lost money.
"Sometimes it's really easy, and in a couple of days we've got everything we need," he said.
"And other jobs we've got are still running after three to six months."
On Monday, member for Gilmore Ann Sudmalis said she had been contacted by numerous South Coast residents who had fallen victim to phone scams.
"If you receive a call that informs you of a returned cheque from a bank error, or a lost taxation refund, please be aware this is almost definitely a scam," Mrs Sudmalis said.
"Some residents have reported to me that the person calling knew their full name, their address and even their birth date."
The current round of scam calls seemed to have a 08 area code, Mrs Sudmalis said.
Mr Patterson said residents should take an "if it's too good to be true, it probably is" approach to phone offers. He said many phone fraud victims were elderly, sometimes suffering from mental illness.
Mrs Sudmalis urged residents to check the caller's authenticity by calling Scam Watch on 1300 795 995 or by going to scamwatch.gov.au.