I just took a call from an 'unavailable' number which was a recorded message telling me that I was in line for a £1000 bonus on my private pension. I declined the offer to 'press 5 to hear more' and hung up and Googled.
It looks like its a marketing thing, and whether they ask for personal details I don't know. Just thought I'd pass this on as I haven't heard of this one before.
Whenever I get these calls now I report them to the Information Commissioners Office www.ico.gov.uk. They may not be a scam but if they are ringing you when you haven't given them permission then they are breaking the code of conduct.
I used to report them to the Telephone Preference Service but if you don't have the callers phone number you can't register the complaint.
That's a new one. I wonder what happens when you press five. Perhaps you get a human or maybe it transfers you to one of those incredibly expensive O9 numbers and you wouldn't know until you got your bill.