Как перевести на английской язык предложение 'Вы бы нечего не перепутали если бы были внимательны'

You would not confuse anything if you were attentive.

Ann: Good morning. My name is Ann. I was here yesterday? Do you remember me?

Shop assistant: Good morning Ann. Yes I do. What is wrong?

Ann: Yesterday I bought this dress form your shop. I did not notice that I picked the wrong size. Can I take the right one?

Shop assistant: Let me see, if there is a size which you want, I shall give.

Ann: Thank you.

Shop assistant. No, sorry, there is not. You would not confuse anything if you were attentive.

I must look for it in another our shops. If there is, I shall let you know.

Ann: Oh, thank you very much.

Shop assistant: You are welcome and be more attentive.