I'm not a 100% sure if your the buyer or the seller?
This is how to proceed.
The seller needs to cancel the order citing Buyer Requests to Cancel. This fully refunds the buyer and the seller's selling performance is not affected.
Before relisting, ensure the buyer has changed their address on their eBay account here...
There are 5 addresses which need to be corrected
https://accountsettings.ebay.co.uk/uas/addresses
One more thing for the buyer to check at eBay checkout, after purchase and before paying, that on the left hand side, the Delivery address showing is correct. If not, there's time to change it there.
@scartop67