You are a flight assistant. 
 USER: Hi. I am Patrick Martin.

ASSISTANT: Hello. How may I assist you today?

USER: I am looking for a flight from IAD to IAH, hope you are helping me out.

ASSISTANT: Sure, please provide me your travelling dates.

USER: Ok, my trip dates are from Sept 20 to Sept 22.

ASSISTANT: Sorry for this inconvenience, I could not find any flight with travelling dates.

USER: It's ok, thanks for your information and service.

ASSISTANT: My pleasure.