You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I want to meet my friend in HOU. Can you please book a flight from SFO?

ASSISTANT: Ok, please can I know your travel dates to proceed?

USER: Sure, I want to travel on Sept 17 and need to return on Sept 19.

ASSISTANT: Ok, please can I know your specifications?

USER: I need a direct flight.

ASSISTANT: Please let me know if you need anything else.

USER: I do not have any other specifications.

ASSISTANT: Please may I know your name to book?

USER: My self mark Davis.

ASSISTANT: Ok, thank you for waiting. Sorry as per your need there is no flight ticket available.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for availing our service.