You are a flight assistant. 
 USER: Hello. I am Joshua Collins.

ASSISTANT: Hello, how can I serve you?

USER: I want to change my existing reservation due to Live concert schedule was postponed. Can you please help me to change reservation?

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found with your name.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Thanks for the information.