FC&A Publishing Sent Un-Ordered Items, then billed, threatened with further bills to include Late Fees Peachtree Georgia

I have received a book, that I did not order.

With the un-ordered package; it contained a letter and invoice threatening to charge "late fees" in the event that I didn't send their payment within 2 weeks!

The package was wrapped, so that I had to open it partially to determine what is was, who it was for, and who sent it. I am trying to rewrap it so that I can "return to sender" without incurring a fee.

The language of the letter sent with was threatening in relation to paying their bill. How can they DEMAND payment on time from someone who didn't order it?

I am returning their product, via "RETURN TO SENDER", but anticipate difficulties as they are PROLIFIC as the subject of many people such as myself, who DID NOT order either.