T: Good morning, sir. May I help you? P: Yes, I want to __________________ to an earlier train. T: Please hold on a moment, I will check whether the earlier train still________________. P: Sure. T: You can change your ticket. Can I have your passport, please? P: Yes, here you are. T: The changed ticket fare is 15 CNY dearer than your original ticket. So you have to pay the __________________. (The changed ticket fare is 20 CNY cheaper than your original ticket. We will return you the _____________________.) P: Of course. This is 15 CNY. T: This is your ticket and passport. Have a nice day.