不出意外楼主的机票是T或者L仓位的，国航官网上面的这两个仓位是不可退票的。楼主在买票的同时已经统一了国航的T&C，不然是不能付款的，尽管在你的机票上没有打上具体的T&C
如果楼主仔细看是有一条When a ticket (including ticket that has been changed) contains a fare based on which the ticket is non-refundable, no matter whether or not the ticket has been used, all fees that have been collected by Air China (including fuel surcharges) will not be refunded.
国航跟你说的可退的70几块钱是机场相关的费用，具体大概樟宜机场28块的安全服务，新加坡政府的Levy 6.10，国内人民币90块的机场建设费。
