I agree. It sounds like the retailer in this situation doesn't understand that particular product that they sell very well. And I agree with the OP in that he was going by their guidance, one of the things he's paying for what I'm guessing isn't an inexpensive bike. In a perfect world the OP would have refused the bike when the shop received it and he discovered it was too big, but that ship has sailed. An unfortunate situation, but I think ultimately the shop should rise to the occasion and make things right.