You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Ryan Thompson here. I need to visit Denver to attend a business meeting so please help me with flight ticket booking from Boston.

ASSISTANT: Sure, please provide me your travel dates.

USER: Sure, I would like to travel on dates of 07/19 and 07/21.

ASSISTANT: Can I have your airport codes please?

USER: Sure, I need to travel from BOS to DEN.

ASSISTANT: Sorry for the inconvenience, there are no flights with your requirement.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Thanks for choosing us.

USER: Most welcome.