Yes, you can cancel a flight and get a full refund from United by calling their customer service at 1-888-829-1467. You will receive a full refund if you cancel within 24 hours of booking, as must issue a full refund in this timeframe.United ' cancellation policy states that you can receive a full refund as long as you cancel your booking inside the 24-hour window which is when you first made your booking. After the 24-hour period has elapsed, you won't be able to receive a full refund.United provides a flexible 24-hour cancellation [$+$+1-888::829::1467.] policy.