You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: Jeffrey Collins here. I want to travel from DFW to IAD for attending a Seminar. Can you please help me for booking the flight ticket?

ASSISTANT: Please mention your travelling dates?

USER: My travelling dates are from 07/22 to 07/24.

ASSISTANT: Please be on hold for a moment.

USER: Ok, I will wait.

ASSISTANT: Sorry Collins, due to heavy tornado there are no flights running on your route.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for reaching our service.