I went through that about a year or so ago.In my case,it was a purchase i made,but much larger than i had ever made before,so they flagged it and would not process it until i confirmed it.That incident showed me how clueless i was at the time though,because when they called,they just said they were the fraud unit from my bank,and i willingly gave them all the info they asked for,which included my full SS#.As soon as i hung up the phone,i realized that could of been anyone,so i rushed to call the bank and verify the number that had called me,luckily it was legit,but it definitely made me aware of how easy i could of been screwed.