Requesting payment for refused and book returned via USPS

I have called over 6 months ago to cancel any further issues of this book and I received a volume in March and I wrote refused on package and returned via US mail. I handed it directly to a postal delivery person who scanned the item and took the book. Now I am getting a bill for a book not accepted. This is the second notice so my account needs to be updated that book was refused and returned.