United offers a "24-Hours cancellation policy", allowing travelers to cancel their reservations by phone at +1-877-590-0011 (OTA) within 24 hours of booking and receive 100% refund, regardless of the fare type. https://myrbkc.rbkc.gov.uk/forums/support-forum/939d4462-68da-ef11-a81b-000d3ab4fcdd