You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I best aid you?

USER: Having an important work at my office, I want to reschedule my journey dates. Please aid me in changing the reservation with the name of Joseph Williams.

ASSISTANT: Sure, I am here to aid you.

USER: Thank you.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to inform that, there is no active reservation found on your name.

USER: Ok, thank you for your information.

ASSISTANT: Thanks for approaching us, have a nice day.