You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Jennifer Green here.

ASSISTANT: How can I assist you today?

USER: I would like to attend a conference in San Francisco, can you please reserve a flight ticket from HOU to SFO?

ASSISTANT: Sure, will you mention your travelling dates please?

USER: Thank you, my departure is on Sept 19 and please book my return ticket also on Sept 21.

ASSISTANT: Do you have any specifications?

USER: Yes, please book my departure flight at the time of evening.

ASSISTANT: Please give me a moment.

USER: Sure, take your time.

ASSISTANT: Thanks for waiting, there is no flights found under your preferable details.

USER: Oh! Sad to hear that. Anyway, thank you for the information.

ASSISTANT: Welcome, have a great day.