You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I aid you?

USER: I want to change my existing reservation due to postpone of my document verification. Can you help me?

ASSISTANT: Sure, please let me know your name to check the reservation list and revert you.

USER: My name is Kimberly Lee.

ASSISTANT: It's unfortunate that we did not find any reservation by this name.

USER: Ok, thank you.

ASSISTANT: Thank you for choosing us.