You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I'm Jeffrey Robinson. Due to the postponement of event held in Houston, I would like to change my existing reservation. Could you help me out changing my existing reservation?

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry Jeffrey, there is no reservation found under your name.

USER: That's ok. Thank you.

ASSISTANT: Thank you for approaching us, have a good day.