You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: My convocation is going to held in Boston, can you please book a ticket?

ASSISTANT: Sure. Please tell me your travel dates.

USER: My travel dates are 08/16 and 08/18.

ASSISTANT: Can you let me know your airport codes?

USER: My airport codes are DFW to BOS.

ASSISTANT: Before proceeding, please tell me your name.

USER: My name is Andrew Lee.

ASSISTANT: Andrew Lee, there are no flights available with your requested dates.

USER: No problem. Thank you for checking.

ASSISTANT: Thank you for reaching us. Have a nice day.