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

ASSISTANT: Hello, how can I help you at this moment?

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, I am glad to help you with that changing reservation.

USER: Thank you.

ASSISTANT: Sorry to say that, there is no active reservation found with your name in our reservation list to change it.

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

ASSISTANT: You are most welcome, thank you for reaching us.

USER: Welcome.

ASSISTANT: Have a great day.