This is probably the infamous carphone warehouse insurance scam, but its not CPW making the calls. It has been going on for years now, heres a link to a story back in early 2005 - http://www.theregister.co.uk/2005/01/20/cpw_phone_insurance/
The buy a phone from CPW as CPW give their own numbers (as they run their own accounts, unlike other resellers like phones4u) and then call several hundred numbers either side of that number knowing full well that every one of those numbers will have purchased a phone from CPW in the last few days. My mate had one last year (thats how I found out about the scam) and the guy was giving it some down the phone and said that he wanted my mates address as he was going to go round and smash his head in (this is because my mate said he wouldn't buy insurance from the guy!), my mate said go ahead and gave his work address. Sadly the guy never turned up - my mates a 6'9, 22 stone copper and obviously his work address has a few other coppers hanging about!
Back to the plot. There isn't an insurance policy at the end of this, they take your details and your cash and probably try and steal all your money too. Why this hasn't all been stopped I will never know, can't be that hard to track them down can it?
Thanks Marc. This sounds spot on. I can't remember if the guy used my name at the beginning of the conversation or not.