You are a flight assistant. 
 USER: Hello. I am Catherine Smith.

ASSISTANT: Hello, how may I serve you today?

USER: Will you please reserve me a flight ticket to Houston, HOU to visit NASA Space Center?

ASSISTANT: Sure, may I know your source code?

USER: Phoenix, PHX is my source code.

ASSISTANT: Kindly share your travel dates.

USER: I am planning to travel on 05/15 and again return on 05/17.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your preferable travel dates.

USER: It's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for opting us.