The postage for an item was more than expected. The buyer is willing to pay the extra amount but I don't know to send him a payment request or another payment request through eBay.
It's not something you can do through eBay unless you cancel/refund and relist. You'd have to use something like Paypal. But strictly speaking it's actually against ebay's rules to charge buyers more postage than was on the listing.
You cannot invoice for additional postage after the item is sold through an eBay listing --- between the buyer and you to make suitable arrangements: orrelist with correct Postage for the Buyer to purchase again.
