You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you out?

USER: I am Frank Wright want to visit Houston, can you book a ticket from SFO to IAH?

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: Sure, my travelling dates will be 04/22 and 04/24.

ASSISTANT: Sorry, there are no flights found in our database.

USER: That's ok, thank you.

ASSISTANT: Thank you for reaching us.