False delivery date before purchase

Can someone please explain some math to me? My order was paid for on the 19th of March. The site says the order will be shipped in 9 to 11 days from the date of payment, but my expected delivery date is the 16th of April. Unless I'm wrong (even if we remove weekends and public holidays) that's more that 11 days. So, you took my money under false pretenses and now I have no way to cancel my order and get my books from a supplier who can actually deliver on time.