What can I do for you? May / Can I help you? 你要买什么？
　　I want / I’d like a pair of sports shoes for my son.
　　我要为我儿子买双运动鞋。
　　How much is it? 多少钱？
　　That’s too expensive, I’m afraid. 恐怕太贵了。
　　That’s fine. I’ll take it. 很好，我买了。
　　How many / much do you want? 你要多少？
　　What color / size / kind do you want?
　　你要什么颜色/多大/什么种类？
　　Do you have any other kinds / sizes / colors?
　　你有其它种类/尺寸/颜色的吗？
　　I bought this blouse here last week, but there seems to be something wrong with it.
　　我上周在这儿买的罩衫，好像出问题了。
　　Can you change it? 你能换一下吗？
　　I insist that you give me my money back.
　　我坚持要求退钱。