You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I'm Jack Robinson.

ASSISTANT: How can I help?

USER: I had planned to visit a place for a vacation, but it has been postponed.can you change my existing reservation?

ASSISTANT: Ok Jack, wait a moment please.

USER: Ok.

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

USER: Ok. That's not a problem.

ASSISTANT: Thank you for contacting us, have a nice day.

USER: Thank you for your help.