I returned a book to Bottom Line Books along with an additional book they had sent me. I am still mistakenly receiving their bill along with annoying form letters saying I still owe them. I have since mailed them back one of these annoying form letters they sent me with bold writing from me informing them I returned not only the book they're billing me for but I also sent back another book they sent which I did not want. I also copied them on the proof of delivery to their Iowa address and the date it was delivered. This proof of delivery was directly from the US Postal Service, so they have this copy. I want them to STOP billing me immediately.