Question Author
Thanks to all for your suggestions. I was probably a bit naiive but couldn't resist - and I was only on the line for about 1 and a half minutes max so even if I've been conned I would hope I don't go bankrupt!
There is still the basic How It Works question though - is it possible to tap in to other people's messages in that way by a technical quirk, or is it impossible and therefore would have to have been a con?
teash - Fylde Coast, by the way!