When an eBay buyer wants to change the address after paying, the safest route is usually to cancel the order at the buyer's request and let them buy again. Posting to an address not on the order weakens your evidence if the parcel goes missing. Fix incomplete addresses by message before printing a label.
Good eBay buyer message templates are short, specific and kept inside eBay messages. Below are templates for dispatch, delays, out of stock items, address checks, returns, refunds, damaged items and missing parcels, with the rules to follow: no contact details or offers to trade outside eBay, and a reply within a working day.
To cancel an eBay order as a seller, open the order in Seller Hub, choose Cancel order, pick the true reason and confirm; eBay refunds the buyer. A cancellation the buyer asked for, an unpaid order or an address problem does not count as a defect, but cancelling because you are out of stock does.
An Amazon tracking number on an eBay order usually comes from a seller buying the item on Amazon and having it sent to the eBay buyer. eBay's drop shipping policy does not allow that: buying from another retailer that ships directly to your buyer is not permitted. Where Amazon tracking is used, it often fails eBay's carrier checks too.
To add a tracking number on eBay, open the order in Seller Hub, choose Add tracking number, enter the number and select the carrier that actually carries the parcel. Do it as soon as the parcel is scanned: the carrier scan inside your dispatch time is what protects you from late delivery marks and item not received cases.