How to cancel a Korean Air flight without paying any fee?

How to cancel a Korean Air flight without paying any fee?
In case of Korean air cancellation within 24 hours of purchase, the traveller is not bound to pay any cancellation fee and is also eligible to get a full refund. This rule applies to all ticket types and destinations. To get the advantage of free cancellation, a traveller will likewise need to keep a gap between seven days from the date of takeoff when cancelling the ticket.