eBay

I sold an item at full price, but it should have been lower as the customer asked for a lower price in 'make an offer'. How can I rectify eBays mistake? I cannot talk to eBay help, just comes up 'fix it yourself' answers. No help.

I have sold an item I also have for sale in eBay. Now I need to cancel/delete that item in my store and I cannot see any simple way of doing that.

how do I send an invoice to a customer that have bought several items and want combined postage?