I'm a little confused on early booking.

Dear DRPHIL321,
Thank you for enquiry!
If you choose "pay later", you can pay for your tickets through other ways or just make a later payment online. But we only purchase the tickets for you after we receive your payment.

You can change the ticket. if you made the changing before you pay, there is no service fee. But there are service fees charged by us and the railway station if you change your ticket after you make the payment (which also means we have already purchased the ticket for you).

We want to remind you that tickets are put on sale 20 days in advance, and you may need to make early changing, as some tickets are sold out quickly.