United Airlines has a 24-hour cancellation policy. If you book a flight at least seven days before departure and cancel within 24 hours, you qualify for a full refund with no cancellation fees. For assistance, you can contact their customer service at 𝟭-𝟖𝟖𝟖-𝟖𝟐𝟗-𝟏46𝟕 or 𝟭-𝟖𝟖𝟖-𝟖𝟐𝟗-𝟏46𝟕.