I believe the federal law, the Fair Debt Collection Practices Act (FDCPA), only applies to Credit Collection Agencies, not the actual company that extended the credit to you. Many states, but not all, have enacted legislation that applies to the original creditor.
I am sure you can look up the state information online, but I have a book by NOLO, “Solve your money troubles,” listing the various states. IT is a good book, perhaps your local library has it or can get it on loan. So if World Financial loaned the money or extended the credit, what rules apply to them may depend on the state you live in.