I don’t have my change back yet.

还没有找我钱呢

I already paid

我已经付钱了

May I have the form for tax refund?

能给我张退税表吗?

Where can I get a form for tax refund?

我在哪能得到退税表

Do I have to declare?

我要申报吗?

Will I have any difficulties with customs?

我过海关有什么困难吗?

I found a stain here

这有个污点

Could you exchange this, please?

能换这个吗?

Could you change it for a new one?

能换个新的吗?

I’d like to return this

我想退掉它

Can I have a refund?

能退给我钱吗?