You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you at this minute?

USER: I want to book a flight ticket from OAK to IAH. Can you help me in that?

ASSISTANT: Sure, I am here to help you with that. Can I know your travelling dates?

USER: My trip dates are Apr 19 to Apr 21.

ASSISTANT: Do you have any other specifications?

USER: Make sure that my depart and arrival should be in the afternoon.

ASSISTANT: Sorry to say that, there are no flight's available based on your travelling dates. May I know your name?

USER: Myself Richard Rodriguez.

ASSISTANT: Thank you for reaching us.

USER: Thank you.