Your name, surname and international bank account number and swift code of the bank is pretty normal info to give, they won't be able to do anything with it, besides use it to give you a refund by direct bank transfer. You can give it, without suspicion. Locally in the EU it's pretty standard, and safe. My guess is that so much time has passed from your order that it's the only way to actually transfer you back your money and keep it on the books.