I'd like to change my reservation on Flight number AR880 on the 16th of this month. 我想更改我预订的本月16日机号为AR880的航班。

Ok. 好的。

Can you change the reservation then, please? 能请你修改一下预订吗?

I'm afraid it'll be difficult for him to make it at that time. 恐怕这个时间对他来讲有点儿困难。

Would you cancel this reservation please, and make it for the same flight tomorrow? 请取消这项预订，改为明天同一班的飞机好吗?

Cancel the ticket for Flight NC 337 and book one seat on the same flight tomorrow. 取消今天的337次航班，改订明天的同一航班。