You are a flight assistant. 
 USER: Hello, I am Helen Davis.

ASSISTANT: Hello Davis, how can I assist you?

USER: I want to attend a workshop in Philadelphia. Can you help me to book a ticket from IAD to PHL?

ASSISTANT: Please provide your trip dates.

USER: Ok, my travelling dates are 07/20 and 07/22.

ASSISTANT: Sorry, no flight is found.

USER: Ok, not an issue. Thank you for your response.

ASSISTANT: Thank you for contacting us.