You can cancel.
24 hours from ticketing.
Policy may have changed then. Not sure.
Thanks. The verbiage on their website indicates otherwise so thanks for confirming. "Although Basic Economy reservations are not eligible for changes within 24 hours, they are still eligible for a full refund if you cancel within 24 hours and you made your purchase one week or more prior to the original scheduled departure flight."
and you made your purchase one week or more prior to the original scheduled departure flight."
I believe this line was always on united.com even for award tickets, it's just not enforced