If a collection agency receives a request for validation they can not continue to collect the debt or report the derogatory account to the consumers credit file.

Fair Debt Collections Practice Act:

§ 809. Validation of debts
(b) If the consumer notifies the debt collector in writing within the thirty-day period described in subsection
(a) that the debt, or any portion thereof, is disputed, or that the consumer requests the name and address of the original creditor, the debt collector shall cease collection of the debt, or any disputed portion thereof, until the debt collector obtains verification of the debt or any copy of a judgment, or the name and address of the original creditor, and a copy of such verification or judgment, or name and address of the original creditor, is mailed to the consumer by the debt collector.
Collection activities and communications that do not otherwise violate this title may continue during the 30-day period referred to in subsection (a) unless the consumer has notified the debt collector in writing that the debt, or any portion of the debt, is disputed or that the consumer requests the name and address of the original creditor.
Any collection activities and communication during the 30-day period may not overshadow or be inconsistent with the disclosure of the consumer’s right to dispute the debt or request the name and address of the original creditor.