fees can be necessary depending on the type of fare

Does Delta give you a refund? Absolutely, Delta Airlines accepts refunds for cancellations made within 24 hours of purchase (us TelephoneBattery. You will receive a 00% full refund right away. After this period, surcharges or other fees can be necessary depending on the type of fare.

Source: https://www.crmportalconnector.com/developer-network/forums/general-discussions/need-help-what-is-expedia-cancellation-policy-no-wait-time