UA may still win this case, or at the least not be forced to honour the tickets, but mentioning the billing country needs to be a barrable offence in this forum.
It has been well established that the credit card billing address is no more than a billing issue. UA do not tie billing currency to the cardholder's billing address. No airline does, as it would lose them sales opportunities.
To argue "fraud" is to argue that UA MEANT TO OFFER these fares but only make them available to Denmark residents. That is as absurd as it is illegal.