David`s Bridal

I`m curious if anyone has had this problem at David`s:
You try on a dress and it fits perfectly. You don`t take the dress in the store but have them get you a new one-same size, style, etc. When your dress arrives, it`s too small, way too small. So now they tell you it needs alterations. Oh and by the way, they suggested "maybe a little weight gain" as the problem and, in fact there was a weight loss.
Thanks.