THATS EXCATLY WHAT IT IS.
DEBT COLLECTION AGENCY..
Ask them for your "SIGNED IN INK" contract that made the debt valid.
and also for a copy of the contract you signed stating that some entity had been given permission to discharge the debt.
they will try to argue, but they cant, so they have no power.
You can ask, but you aren't getting those things. Unsecured credit card contracts won't have your signature anyway. Use of the account becomes your agreement to the terms. A handful of billing statements obtained from the lender, while proving little, are enough to satisfy debt validation.
"Discharge" of debt is something you do in bankruptcy. Possibly you meant "charge off", which a creditor is REQUIRED to do by federal law. Lender contracts all say the debt can be assigned or sold to any collector they please, so you don't control that either.
When demanding validation it is enough to state that you dispute the debt claim. It's the collector's problem to make meaning of that. Making a shopping list of legal discovery-type items won't enforce your rights, but it will create a road map for defeating you if the creditor decides to file suit.