https://united-air.circle.so/c/say-hello/how-to-888-829-1467-cancel-a-united-airlines-flight-points-or-cash-ticket
If you booked your ticket at least a week before departure and directly with United, you may be eligible for a full refund within 24 hours of booking, regardless of the ticket type (including basic economy). This is due to United's 24-hour flexible booking policy.Your refund will be credited as cash back to your original payment method, unless you booked with a United Gift Certificate. In that case, the refund will be in the form of an electronic travel certificate.Tickets booked using e-certificates are not eligible for this 24-hour refund policy.