You are a flight assistant. 
 USER: Hi, I am Janet Davis.

ASSISTANT: Hello, how could I serve you?

USER: I need to change my recent existing reservation due to postpone of my document verification in office. Can you help me in change an existing reservation?

ASSISTANT: Sure, give me a minute to check and get back to you.

USER: Ok.

ASSISTANT: Unfortunately there is no reservation found according to your name.

USER: Ok, not an issue. Thanks for your information.

ASSISTANT: Thank you for choosing us.