You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you today?

USER: David Hill here. Please help me out in booking the ticket from HOU to DTW.

ASSISTANT: Sure, I am gleeful to help you with that. Can you please provide your preferable dates of travelling?

USER: My trip dates will be Aug 22 to Aug 24.

ASSISTANT: Is there any class preference do you have?

USER: Economy is my class preference.

ASSISTANT: Any other preferences do you want to add?

USER: Return time must be in the morning.

ASSISTANT: Please wait a moment to check the flights on your route.

USER: Ok.

ASSISTANT: We regret to inform you that, there are no flights available for your journey within your departure time.

USER: That's ok, thank you.

ASSISTANT: Thank you for reaching us, have a great day.