Refunded the whole order instead of part shipping

I was trying to do the decent thing and refund part of the shipping (£2.50), but this glorious Amazon Seller Central defaults all the products and shipping when one clicks on refund. What happened was that I refunded the whole order, plus shipping, plus the £2.50 I was trying to refund initially. I only realised this when I combined a multiple order and went to refund the excess shipping realising the whole order would be refunded. Any ideas how I go about getting the accidental refund back? Seller Support were amazing once again with the cut and paste and incorrect information, so I am hoping someone on the forum has experienced this before. Thanks