I uploaded a low value item on ebay.co.uk. post was recommended which I selected. A buyer purchased item and paid £1.70. I had to pay another 87pence before being able to access to the QR code/pre-paid delivery label. Post office, would not accept as 'large letter'. In order to post by the deadline I have paid a further £4.05. How do I get credit for the 87p (money deducted from my ebay account) and funds the buyer has paid £1.70)?