我报了GRE的3月份机考,但是现在还没开始准备,所以想要取消6G来报10G,请问怎么取消?

应该是要写信到ets,而且不能全额退钱.帮你搜的：
能退约700RMB
以下是ETS的回信：
We have processed your request for a refund. A refund check in the amount of US $ $102.50 will be mailed within six to eight weeks to the address you provided. Please allow sufficient time for mail delivery