Landmark America II, Junk debt buyer suing me Warren Ohio

Landmark America wrote to tell me they had bought a loan I had with a local bank and now wanted immediate payment for the FULL amount owing. I disputed that I owed anything but if I did would they tell me what the amount is. I never heard back from them until I got a summons for the full amount. I know this company buys distressed or junk debts for pennies on the dollar so I asked them again to tell me what I owed and what they paid to buy that alleged debt. No response.

My question is this. When a company buys a junk debt can they legally come after the debtor for the full amount or only seek to get back what they paid to purchase the debt plus the usual interest and late fee's etc?

Jonathan
Orlando, Florida
U.S.A.