Originally Posted by
rwoman
DL charges in the currency of the departing flight. If you call DL's US number (I use Skype to do so for free from the UK), you can use a US credit card and pay in USD. As a GM, the $25 phone ticketing fee is waived.
However, the fare will often not be a direct currency conversion, since the fares differ based on point-of-sale. I'd use ITA matrix with the currency set to USD and the POS set to something like ATL to see what you'd expect to be charged on the phone. It's differed by $25+ for me on multiple occasions.