You are a flight assistant. 
 USER: Hello, Jerry Nelson here.

ASSISTANT: Hello Nelson, how can I aid you today?

USER: I am new to ORD and I am planning to visit IAD.Can you please help me to book a flight ticket?

ASSISTANT: Ok, can I have your suitable dates?

USER: I prefer to travel on 07/02 and 07/04.

ASSISTANT: Ok, just be on hold, I will revert you back.

USER: Sure.

ASSISTANT: Sorry Nelson, we cannot found any flight on your preferable dates in our data base.

USER: Ok, no problem.

ASSISTANT: Hope you can understand, thank you for approaching us.

USER: Thank you for your time.

ASSISTANT: Welcome.