You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Charles Davis.

ASSISTANT: How can I assist you?

USER: I am planning for the trip to Philadelphia to visit the famous place that is Ghirardelli Square. Can you help me in reserving a flight ticket?

ASSISTANT: Sure, can I know your travel dates?

USER: My travelling dates are 04/16 to 04/18.

ASSISTANT: Please share your airport codes.

USER: I will fly from IAD to PHL.

ASSISTANT: Sorry, there is no flight available on your requested dates.

USER: No issue, thank you.

ASSISTANT: You are welcome.