Complaint Review: Knetbooks

First they claimed I sent back a damaged book and they were charging me full price ,new, for a used book. I sent two used books back in time. They claim one was water damaged. Ups said no damage reported to package. One supervisor refused to do anything about it. Two months later they sending me letters saying book never returned that I must pay for reolacement. That to much time had passed to return it. Also strange was that when I told them I want to see proof the book was damaged they told me if I didn't pay the book would be destroyed in ten days or less. They are constantly eemailing me. They refuse to give me information to file a lawsuit.