If a reservation is made at least seven days before departure, United 24 hour cancellation policy allows for a full refund for tickets that are cancelled within 24 hours of their purchase. Basic economy tickets purchased more than a week before departure and not cancelled within the 24-hour window are not eligible for a refund under United's 24-hour cancellation policy. Cancelling a ticket for basic economy On United flights, a basic economy ticket cannot be changed unless it is done within 24 hours of purchase and was bought a week or more before the original departure date.
https://airlinespolicy.com/can....cellation-policy/uni