Validation notice
The notice a debt collector must send that names the creditor, itemizes the amount and gives you 30 days to dispute.
A debt collector must give you a validation notice in its first contact or within 5 days after. It names the creditor, shows the current amount with an itemization of interest, fees, payments and credits, and gives the end date of your dispute window.
If you dispute in writing within 30 days of getting it, the collector must pause collecting the disputed amount until it sends verification.