A round trip between Paris and Zurich ended up costing a traveler named Sebastien far more than he expected, after Swiss International Air Lines told him at the gate that his reservation had never been issued, according to reporting by the Swiss outlet 20 Minuten.

Sebastien booked his outbound and return flights on July 20 for a total of 269.45 euros and received a payment confirmation, though he later said the confirmation email looked different from what he normally receives from the airline. He called customer service to check that the payment had gone through and says he was told everything was fine.

When he arrived at Charles de Gaulle airport for his flight, staff informed him that his booking had in fact been cancelled and had never been properly issued. To travel, he was told he would need to purchase a new ticket, this time for 807.67 euros, roughly three times his original fare. He says he had no way of knowing beforehand that the reservation had fallen through, since the original charge was not refunded to his card until July 31.

Sebastien contacted the airline again to request reimbursement of the 538.22 euro difference between the two bookings. Swiss initially offered to cover that amount in travel vouchers rather than a cash refund, and the airline's internal review of what it called a highly unusual chain of events took some time to resolve.

The airline has since acknowledged what it described as a technical glitch, said it regrets the error, and confirmed it will refund the 538.22 euro difference to the passenger.

This account draws on reporting by La Dépêche.