You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I'm Andrew Phillips.

ASSISTANT: How can I help you Andrew?

USER: I need to attend a meeting in Houston.Can you book a ticket from PHL to IAH?

ASSISTANT: Sure. Please let me know your travel dates.

USER: The departure is on 01/25 and return is on 01/27.

ASSISTANT: Andrew, there are no flights available at this moment.

USER: That's really sad. Anyways, thank you for your help.

ASSISTANT: Thank you for reaching us.