I had a call from a chap with an Indian accent purporting to be from Westpac bank and asking for some "personal details to confirm my identity". The call was definitely an overseas call as it had that annoying satellite delay. When I asked him what the call was about, he said that he couldn't say until my identity was confirmed. He also gave me a phone number to call to verify his authenticity. Obviously, the number he gave me would have just reconnected me with him. Instead, I looked up the Westpac number from the internet and called them. They said that WESTPAC DO NOT HAVE ANY CALL CENTERS IN INDIA. Busted!
It's been said many times before but worth repeating
DO NOT GIVE OUT PERSONAL DETAILS TO ANYONE WHO CALLS YOU ON THE PHONE FOR ANY REASON WHATSOEVER.
Independently research the phone number of the organisation that the caller purports to be from and call them to verify if there is an issue.
I have had the same call that Ian got and I know several people who also got one of those calls, including my 85 year old mother in law. It put the fear of God into her, but fortunately she had the presence of mind to refuse to answer their questions and called me instead.
Also, I no longer make donations to charities from telephone solicitations for the same reasons.