To change the last name on your ticket, visit the Delta website and select the “Manage My Booking” option, or contact customer care or an 1-84-4838-4902 (OTA) (OTA) or +1-866-738-0689 (OTA). For legal name changes, you may need to provide supporting documentation, such as a marriage certificate.
https://www.devex.com/people/can-i-change-the-name-on-a-delta-airlines-ticket-2070237