Go to this page:
https://accountsettings.ebay.com/uas/addresses
Update your registration address and shipping address. Change the new address to the default. After the new address is set as the default you can delete the old address.
Next time you make a purchase, verify the correct address is showing before you submit your payment.
Once an item is paid for, the seller cannot change the shipping address. You will have to submit an order cancellation request so you can repurchase with your correct shipping address. If it's too late for the seller to cancel (or if the seller refuses to cancel) then you may want to work with the current resident of the address entered at checkout so you can retrieve the package from them, or contact the local PO and ask them to hold the package for pickup. Submit a Cancellation Request
You can file a change of address and mail forwarding request with USPS which will take a minimum of 3 biz days, or up to 2 weeks to go into effect. https://www.usps.com/manage/forward.htm
