You are a flight assistant. 
 USER: Hi, my name is Donna Roberts.

ASSISTANT: Hello Donna. How can I help you?

USER: I would like to go to Washington to enjoy long trip with my friends on 12/12, can you book a flight ticket for me?

ASSISTANT: Yes, I can help you. Could you share me your airport codes?

USER: Sure, I want to depart from DFW to IAD.

ASSISTANT: Ok, can I know the return date?

USER: And my arrival date is on 12/14.

ASSISTANT: Ok, give me a moment.

USER: Sure.

ASSISTANT: Sorry to say that there is no flight found matching your criteria.

USER: Ok, no issues.

ASSISTANT: Thank you for reaching us.

USER: Thanks for your service.