I've dealt with this situation before. I asked for combined shipping prior to paying for both items. The seller said no, I paid anyways. Seller shipped combined. I asked for a refund totaling the difference, which the seller complied with. I would ask for the difference to be refunded to you, if the seller declines, escalate through ebay. As others have pointed out there are a few avenues you could take if you wanted to pursue further.