Hello. I bought a China dress in your shop this morning.
Yes?
I bought it one size up by mistake.
Oh, did you?
I wonder if you can change it to one size down.
Yes, of course. Will you come with the receipt?
Then I'll come to your place later in the evening, and how late is your shop open?
Until 8 o'clock, ma'am. We are looking forward to seeing you.