If you need to change or cancel a reservation, you can do it at "Ticket Reservation>View/Modify/Cancel".

Viewing, Modifying or Canceling tickets

• Reservations made through the TxBux service are handled in real-time through the internet.
  However, in some cases, due to errors due to browser environment or viruses, users may not be able to verify whether reservation has been successful after credit card payment.
  After making a reservation, customers are urged to verify whether reservation was successful by using the "View, modify or cancel tickets" menu.
• Customers having made reservations as visitors need to provide the credit card number used to make the reservation, or their date of birth and telephone number, in order to use the "View, modify or cancel tickets" menu.
• When issuing the ticket for the reservation, users must present the credit card used to make the reservations.
  This card may be presented to the ticketing officer at the terminal, or, if an automatic internet reservation ticketing machine is installed, users may swipe their card using this machine to receive their ticket.
• When changing reservations, seats may be changed without entering payment information.
  When changing time or bus class, the original reservation is automatically canceled so that you are not billed twice.
  For more details, please contact your credit card company.

Information on cancellation charges for the Inter-city bus ticket reservation service