Knetbooks Overcharged and denied refund Lexington Kentucky

I rented a textbook from knetbooks for one semester because it was cheaper than buying. As it turns out, I needed it for the following semester so I extended the rental. Finals were going on when I was suppose to return it so I did not return it on time. It would have cost me $20 to extend the rental for a little while longer or about $75 to purchase the used book. Before I could send it back, I received an email stating that my credit card was charged to purchase the book. If I returned the book by June 29th, I could get half of the money back. When I looked at my statement, I was actually charged $135 for the used book, not $75. I shipped the book UPS before June 29th but it did not get there by the 29th. When I called to discuss this matter, I was told that I would not get any refund. So not only did knetbooks get the book back to rent again, I ended up paying way over $200 to just rent the book. My advice is to just buy a textbook from another company. It will save you money in the long run and you can sell it when you're done to recoup some of the cost.