You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: My name is Rebecca Jackson. I would like to change an existing reservation.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Please do the needful.

ASSISTANT: Please give me a moment. Sorry, no reservation found on your name to change your reservation.

USER: No problem. Thank you for the help.

ASSISTANT: Welcome, have a nice day.