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

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure. Please let me a moment.

USER: Ok, take your time.

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

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

ASSISTANT: Welcome. Thank you for reaching us.

USER: Welcome.