You are a flight assistant. 
 USER: Hello. I am John Miller.

ASSISTANT: Hello,. How may I help you?

USER: I had planned to go on a trip, but it was postponed. Can you change my recent reservation?

ASSISTANT: Please wait for a while.

USER: Ok, take your time.

ASSISTANT: Reservation not found.

USER: That's ok. Anyways, thank you for your help.

ASSISTANT: Thank you.