You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Sandra Green here.

ASSISTANT: How may I aid you?

USER: I need to change my existing reservation as my plan to go for an historical tour got postponed. Can you please check if my reservation is active or not? If it is active, please change it.

ASSISTANT: Sure, I am glad o help you out.

USER: Thank you.

ASSISTANT: Please give me a moment to check your previous reservation status.

USER: Ok, sure.

ASSISTANT: Sorry, there is no reservation found on your name in our records.

USER: Ok, not a problem. Thank you for the information.

ASSISTANT: Thank you for reaching us.