You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Mark Miller.

ASSISTANT: How can I assist you today?

USER: I want to attend my brother's wedding at Philadelphia, can you please help me to book my flight ticket from DFW to PHL?

ASSISTANT: Sure, can you please share your travel dates?

USER: Nov 9th is my departure date and I would like to return back on Nov 11th.

ASSISTANT: Do you have any class preference?

USER: No, anything is fine for me.

ASSISTANT: Mark Miller, I am sorry to inform you that there is no flight available at your requested dates.

USER: Sad to hear that. Anyway, thank you.

ASSISTANT: Thank you for contacting us.