Yes, was this on a Mastercard or Visa? Mastercard theoretically has more protection since all you need to do is say you didn't have the opportunity to pay in local currency. Visa offers more ambiguity here, but includes protections that prohibit merchants from "using actions or procedures" to get you to choose DCC by default. How much was the value of the transaction? If it's a small amount Citi will likely credit the difference. If it's larger, they can do a chargeback assuming you get a rep in the know about the DCC scam.