SNCF E-TICKET改签

我之前在SNCF上订了2人巴黎往返马赛的E-TICKET 车票, 现在想改在当天下一个班次的火车上,但是进入manage my order里面, 没有exchange的界面, 望游四海旅游高手指点如何改票? 票面条款是显示可以改的,
Loisir reduced fare : Can be exchanged and refunded free of charge up until the day before departure, with a 10 euros administrative charge the day of departure