Ordered a onesie for dd, low price and almost equivalent postage. Ordered extra small but have been sent small/medium on the label which is huge on her. Needed it to embelish for dressing up for book week so it's not going to be much use the size it is tbh. So would I be reasonable to ask seller to send an extra small that I will pay for if she pays the postage? Otherwise I will have to return (pay £4.50 postage) and seller will have to pay postage again to send replacement or refund (I hope). If not, what should happen? Thanks