https://www.eki-net.com/top/tr/guide/receive/
Reserved seat tickets (used with a pass) reserved on this site
If you no longer require your seat, no fee will be charged, but please make sure to cancel the seat reservation from the website.
If you have reserved seats, pass refunds cannot be issued after the train departs.
Reserved seat tickets (used with a pass) that weren't reserved on this site
If you do not pick up your ticket by 21:00 on the day before your boarding date, the reservation will be canceled automatically (free of charge).