I received a notice from an attorney's office in July 2011, stating that I owed money to a credit card I don't ever believe I had. I responded to their request--asking for validation. I did not hear anything from them until mid-February of 2012. When they did respond, it was with an unsigned copy of an agreement plus bills that did not show how the debt was accumulated. I believed they violated fair debt collection practices, so I responded with a letter advising them of this belief along with my original letter and proof of receipt. I got a letter saying they have satisfied their burden. They say the 30-day notice applies to the dispute rather than validation. Is this true? How should I respond to this notice?