You can cancel any flight within 24 hours of booking for a full refund, as long as the flight was booked at least 7 days before departure at +1-833-444-7613(US) OR +1-833-522-9940 Does Singapore Airlines have free cancellation? Singapore Airlines allows cancellations with full refunds within 24 hours of booking, provided your departure is at least two days away +1 833-444-7613 or +1-833-522-9940.
https://www.devex.com/people/how-late-can-i-cancel-my-singapore-airlines-flight-2227011
