You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. What kind of help can I provide to you?

USER: Myself David Garcia.

ASSISTANT: Ok.

USER: I want to book a flight from DFW to IAD.

ASSISTANT: Sure, Can you mention your journey dates?

USER: My preferable dates are from 08/17 to 08/19.

ASSISTANT: Ok, Please wait for a couple of minutes.

USER: Sure, take your time.

ASSISTANT:  Thanks for waiting, there are no flights available at this moment matching your particulars.

USER: Ok, no problem thank you.

ASSISTANT: Thanks for your presence.