I haven't heard of the idea of being free. If you want to change it, it is free, that is, the face value is zero. You need to confirm the travel date and call 95539 to ask if the flight you want is free. If yes, you can prepare the airport construction fee and fuel surcharge, as well as a copy of the front and back of the credit card and a copy of the cardholder's ID card, and pay for the air ticket according to the address he told you on the phone. Because this is a free ticket, not to buy a ticket, but to change it. Change when the mileage is enough. If it is not enough, it will not be changed. There is no such thing as money to make up for it.