Delta 𝔸𝕚𝕣lines provides a 24-hour cancellation policy.+1-𝟖𝟑𝟑-444-𝟕613 If you book a 𝕗𝕝ight at least seven days before departure and cancel within 24 hours of booking (【+1-𝟖𝟑𝟑-444-𝟕613 USA or +𝟷-𝟾𝟹𝟹-𝟻𝟸𝟸-𝟿𝟿𝟺𝟶 】), you are eligible for a full refund without any cancellation fees.
https://www.devex.com/people/does-delta-have-a-cancellation-policy-2229834
https://www.devex.com/people/does-delta-have-a-cancellation-policy-2229273
https://www.devex.com/people/can-you-cancel-a-free-of-charge-2228566
