Составьте диалог на с фразами what size do you want? can i try them on? could you change whats wrong with it? it's the wrong size theatre

-Good Morning!
-Hello!
-What would you like?
-I'd like to buy a dress for going to the theater today.
-What color would you like?
-Hm... I was thinking about something dark. Do you have a dark blue dress?
-Well, let me see. Yes, we have many dark blue dresses. They are very fashionable this spring. 
- Can I try on this one?
- Yes. What size?
- I think 40, but I'm not sure.
-Okay, so here you are.
- Could you change it, please?
-Yeah, what's wrong with it?
- It's the wrong size. I need a smaller one.
- Let me check out if we have the size you need. Yes, we have. Here you are.
- I like it! I buy it!
- Okay, go to the cash desk.