Final answer:
To cancel a segment or an itinerary, follow the cancellation policy of the airline or travel agency. Most airlines allow cancellations online or by contacting customer service.
Step-by-step explanation:
To cancel a segment or an itinerary, you typically need to follow the cancellation policy of the airline or travel agency with which you made the booking. This policy can vary depending on the specific airline, type of ticket, and fare conditions. Most airlines allow you to cancel or modify a booking either online, through their customer service hotline, or by contacting a travel agent. Keep in mind that cancellations may be subject to fees or penalties, especially if the cancellation is made close to the departure date.