Refuse the package upon arrival from the carrier or write "refused" on the front of the package and return it to your local post office.
When a package is refused, notification will be received in the mail from the USPS in the form of postcard notification. This notification will be sent to the address provided by the sender as the return address. The post office will hold the package at the postal location closest to the return address.
Once the sender arrives at the post office, a clerk will present the refused media mail package and ask if you would like to pay postage on the item. Because the package has traveled through the mail twice, both to its destination and returning, it must once again be payed for. If you would like the item returned to you, pay for the additional postage. The post office may retain the item if postage cannot or will not be paid.
Return of media mail is especially common when sending packages through the penal system. Military addresses can also be difficult to deliver.