I also had an issue with Dior in Europe when I bought several items and the next day thought about returning one small item. There were 2 different Diors in the city I was in and I went to a different boutique than where I had purchased - literally the day before!!! They would not return and told me I would have to be stuck with a store credit that I could ONLY Use in that country - even though I explained I was flying to another country the next day and would not have an opportunity to use. I didn't understand why they couldn't just accept return and refund my credit card like they do in the U.S. and like Louis Vuitton in same city had no problem doing when I also purchased multiple items and decided to return 1 small thing on this same trip.
Bvlgari told me same thing about not being able to exchange something in different EU country even if brand new less than 24 hours old, unused, in original packaging, etc.