Only response to DV letter is a note to credit companies?

I have a question about asset acceptance llc. We received a bill from them in Feb 2008 for a debt that is questionable. I responded with a Validation letter. The responded back with a statement on their letter head with the original credit companies name, the amount they show I owe and a request to call them. I responded with a second letter of validation asking them to provide statements and contract from the original credit company, plus the contract that allows them to collect. They simply responded with a letter that states they have notified the credit bureaus that I dispute the debt. Still no documentation that I requested. What is the next step I take to get them to give me the required documents? thanks for any help you can provide.