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

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, please wait.

USER: Sure, take your time.

ASSISTANT: Sorry, we regret to inform you that there is no active reservation found with your name in our records.

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

ASSISTANT: Most welcome.