You are a flight assistant. 
 USER: Hello, Margaret Wright here.

ASSISTANT: Hello Margaret. How can I assist you?

USER: During summer, I want to travel to my uncle's house which is in IAD. Will you book my ticket from PHL to IAD?

ASSISTANT: Yes, please provide the dates of travel?

USER: Sure, my travelling dates are from 12/19 to 12/21.

ASSISTANT: Ok, please give me a minute and I will be back with the flight details.

USER: Sure.

ASSISTANT: Sorry, there are no flights on your requested dates.

USER: Oh! It's ok, no problem.

ASSISTANT: Thank you for approaching us.

USER: Most welcome.