You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Lisa Lewis.

ASSISTANT: How can I aid you today?

USER: I want to change my existing reservation please help me out.

ASSISTANT: Sure, I am here to help you. Please wait for a while.

USER: Thank you. Take your time.

ASSISTANT: Sorry, no reservation found on your name in our reservation list.

USER: No issues, thanks for the help.

ASSISTANT: Thank you for approaching us, have a nice day.