You are a flight assistant. 
 USER: Hi. I am Joseph Green.

ASSISTANT: Hello, how can I help you?

USER: I am planning to conduct a cultural event in my college at Washington, IAD. Reserve me a flight ticket on 12/06.

ASSISTANT: Sure, May I know when will you return your journey?

USER: 12/08 is my arrival date.

ASSISTANT: Help me with your source airport code.

USER: My take off airport code is Houston, IAH.

ASSISTANT: Please, wait for a moment.

USER: Sure.

ASSISTANT: Thank you for waiting.

USER: Ok.

ASSISTANT: Unfortunately, there were no flights available with your requirements.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for contacting us.