Delinquent debts and overdue accounts can be sold to junk debt buyers. Creditors have the right to charge off debts that are delinquent and other overdue accounts and sell those accounts to third-party junk debt buyers and debt collection agencies. When sold, the agency that bought your account is the legal owner and has the right to try and collect the debt. This does not mean they can just do anything they want with the account and still have to follow the FDCPA.
Collectors cannot just add additional interest and fees to the account. They must follow either the original credit contract or state law. If state law exists, then it takes precedence over the credit contract. For instance, some states limit the collector’s fee to certain amount and prohibit collectors from adding additional interest.
It’s in your best interest to check your credit contract and your State and Local Government Laws to see which applies to your situation. Your state’s fair debt collection practices act is another good source to review.