You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Brian Nelson.

ASSISTANT: How can I assist you at this moment?

USER: I am planning to chage an existing reservation, due to heath issue.Can you please help me out?

ASSISTANT: Sure, I will help you with that.

USER: Sure, take your own time.

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Sorry Brian, there is no reservation has found under your name.

USER: That's fine, thank you for your help.

ASSISTANT: Most welcome. Thank you for choosing us.