The FDPCA gives you rights: for example, you have the right to verify the debt and see the contract you signed when you took it on. The debt collector who calls you almost certainly does not have that contract and can't get it. Your original lender might, but they stopped caring about your debt the minute they sold it to a debt-collector.
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Their own IT systems are baling-wire-and-spit Rube Goldberg machines that glue together the wheezing computers of all the companies they've bought over the last 25 years. Retrieving your paperwork is a nontrivial task, and the lender doesn't have any reason to perform it.
Debt collectors are bottom feeders. They are buying delinquent debts at 5 cents on the dollar and hoping to recover 8 percent of them; at 7 percent, they're losing money.
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