I had a buyer purchase a small item from me, free postage, which I duly sent and had proof of postage. However because it didn't arrive at the time they wanted (it was sent at no cost to them by second class) they started an item not received process. I asked them to wait for a couple of days, which they did but then contacted me saying the post had come that day and the item wasn't there, so demanded a refund. I refunded them but then checked the tracking and found it had actually been delivered that day, the buyer is ignoring my messages, I can't find any help from eBay, anything I can do?