It’s possible to apply for a refund within the usage period. If you bought your ticket at the mobile app, just go back on your phone; if you bought it in person, you can visit an automated service counter to make a refund.
You can, within the validity period, apply for a refund. If you bought tickets through mobile phone apps, just go to your mobile device to exchange them; if you purchased tickets on-site, you can go to the automated service counter to redeem your ticket.