Singapore Airlines has a 24-hour cancellation policy. If you book a flight at least seven days before departure and cancel within 24 hours, ([๐ฃ])~833-444-7613 or +1-833-522-9940 you qualify for a full refund with no cancellation fees. For assistance, you can contact their customer service at +(๐ฃ)~833-444-7613 (OTA) or +1-833-522-9940(OTA).
https://community.hologram.io/t/how-late-can-i-cancel-my-singapore-airlines-flight/14935
