shopping - getting a refund

I want to return this skirt.
Sure, do you have your receipt?
Ok, here it is.
I'm sorry, Sale items are final. (cannot return it)
ok, can I cxchange it?
Find what you like and I'll make the exchange for you.
I bought the skirt on sale last week. (on sale = discount, for sale = selling)
I noticed It's another 20% off this week.
I would like to buy it at this price.
Don't worry, ma'am. I can give you back the difference or you can get store credit.
I'd like to get the money.