I am attempting to make a partial refund to a buyer for inconvenience caused with the delivery (insufficient postage). The buyer initiated a refund claim because they didn't want to pay the surcharge, but once we agreed the partial refund, they paid the charge, the item is now showing as delivered, but when I go to make the promised refund, it shows that I cannot make a refund because the buyer has opened a case. I just seem to be going round in circles!! I am relatively new to this, and this is the first time I have been faced with this. HELP!!!!