Contact Amazon and tell them the items never arrived. If the rep won't refund you, ask to speak to a supervisor. Here's the link to use chat:
https://www.amazon.com/gp/help/contact-us/general-questions.html
Or you can call them at 1 (888) 280-4331.
I would report the multiple missing items to the mailbox store. You're paying them for this service, and if there's a theft issue, they should know.