You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I be your helping hand today?

USER: I want to meet my grand parents on their 60th marriage anniversary, can you please help me to book a flight from DEN to IAD?

ASSISTANT: Sure, can you please share me your preferred travelling dates?

USER: I will travel on Dec 12th and 14th.

ASSISTANT: Ok, do you need any lay by in between the journey?

USER: I prefer a direct flight.

ASSISTANT: Ok, can I have your good name please?

USER: My name is Rachel Smith.

ASSISTANT: Ok, may I know your class preference?

USER: I am ok to fly in any class.

ASSISTANT: Do you have any other preferences?

USER: No, I don't have.

ASSISTANT: There are no flights found on your requested dates.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.