If the guy shipped them seperately, then he did nothing wrong but when he combined the shipping, he should have combined the charges. You gave him the opportunity to do the right thing and refund the difference and he chose not to. If his auctions stated that he combines shipping, then I'd leave the negative feedback for the false advertising. If the auctions didn't state it, I'd leave neutral feedback stating that he combined the items but not the charges and leave it at that. Either way, positive feedback was not earned.