You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Katherine Williams here.

ASSISTANT: Hello Williams.

USER: Can you find a flight from IAD to PHX?

ASSISTANT: How can I aid you? Can I know your preferable dates?

USER: My travelling dates are 07/30 and 08/01. Please search a flight with price limit of 200.

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

USER: Ok. Thank you for your time.

ASSISTANT: You are welcome.