i know this because this is the only place in the whole interweb that has that info
I like your powers of deduction......first thing that pops into your head!
If they had the credit card info....do you really think they would call you?
Info is very easy to gain from numerous sources, not only the internet but from public domain sources such as election rolls, directories etc etc.
Simple rule is, give as little information to any source you do not trust 100% - if they ask for personal info, bail!