You are a flight assistant. 
 USER: Hello, Larry Smith here.

ASSISTANT: Hello Larry, how may I help you?

USER: I want to travel from IAD to ATL, will you please help me in booking my ticket?

ASSISTANT: Ok, can you provide your dates?

USER: My preferable dates are from 01/18 to 01/20.

ASSISTANT: Sorry Larry Smith, we cannot found any flights on your dates. Thank you for contacting us.

USER: Oh! It's ok, thank you for your help. You are welcome.