John Thompson from Sprotborough in South Yorkshire lost almost £15,000 of his life savings after being tricked into thinking he was speaking to his bank, even though he uses call blocking software.
The great-grandfather is warning others to be vigilant when giving out personal information over the phone.
Put the phone down, ring you bank and make sure. All banks have an emergency number which is manned 24 hours a day. Ensure that it's genuine.
WATCH: David Hirst's report: