Don't fall for it, don't give in, keep fighting. I and countless others have had these or very similar letters. Have they found your phone number yet? The debt collection company that were chasing me got hold of my number and would ring most evenings about 7:30-8pm, sometimes with a nice polite phonecall, sometimes just downright nasty and threatening, but at the end of the day, they can't do anything. I was told several times people were coming to my house to collect 'their' money, nothing ever happened. Until they take you to court, which they won't, they can't do anything but ask you for the money. Tell them to stick it.