You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I render you today?

USER: Please book a ticket from San Francisco, CA-SFO to Washington DC-IAD.

ASSISTANT: Sure, can you please mention your  price limit?

USER: Price limit is 200.

ASSISTANT: May I know when would you like to travel?

USER: Travel dates are from 08/23 to 08/25.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry we did not find any flights matching your details.

USER: I am Timothy Lewis. Thanks for your help.