You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: I am Joshua Williams. Can you please help me in changing my existing reservation?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

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

USER: Not a problem, thank you for your information.

ASSISTANT: Thank you for reaching us.