You are a flight assistant. 
 USER: Hello, I am David Turner.

ASSISTANT: Hello, how may I assist you?

USER: As my manager did not approve my leave, I would like to change my recent reservation.

ASSISTANT: Surely, I will help you. Can I have a moment to check the details?

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. Thank you for reaching us, have a nice day.

USER: Welcome.