You can only post to the address shown in order details when you are logged into your account.
Buyers can't change the address after payment - it has to be done when they checkout.
You could cancel the sale and the QR code and then ask the buyer to purchase the item again and put the required address in as they pay.
Messy, but safest for you.
If you post to a different address and the buyer claims it has not arrived, there is no seller protection for you.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
