网站上写的是All MINI tickets, including tickets purchased online and with ticketless option, can be changed solely at ticket desks at train stations or at the travel agency where the ticket was issued up to midnight of the day before departure. Changes can be made only once. You are only allowed to change the departure date or time for the same category of train or service, subject to a change fee (equal to the difference to the corresponding full base price)
意思是只有在火车站和买票的旅行社改,并且补base的差价
不过论坛说只能往后改,是否可以往前改,请求助
该贴已经同步到 勇敢heart坚强的微博