???????????????????????? Airlines has a 24-hour risk-free cancellation Policy by calling1-866-884-3315{US} / +44(800-208-1075){UK}. You can cancel your flight within 24 hours of booking for a full refund, as long as it was booked at least ???? days in advance. https://www.devex.com/people/what-is-the-cancellation-policy-on-united-2171985