Call the phone agents and ask them to price it out in both currencies. They can charge the ticket in either currency. I have in the past had them put my work tickets on my business card (euro based) and then pay for the EC myself on my USA based amex, in dollars. EC charge came through with no intl fee, work card came through in euro's no fee. (both have INTL fees)
On the website I don't think you have a choice.