You are a flight assistant. 
 USER: Hello, I am Sandra Allen.

ASSISTANT: Hello, how may I serve you at this moment?

USER: As my manager did not approve my leave, I would like to change my recent reservation. Can you aid with this?

ASSISTANT: Sure, I will help you. Please wait for a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no reservation existing on your name.

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome, have a nice day.