You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Can you please change my existing reservation as my planed holiday trip got postponed due to some issues?

ASSISTANT: Sure, may I know your name please?

USER: I am Christine Lee.

ASSISTANT: Ok, please wait a minute.

USER: Sure.

ASSISTANT: Sorry Christine, there is no reservation found under your name in our database.

USER: Ok, no problem. Thank you for your response.

ASSISTANT: Most welcome.