You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: Nicholas Harris here. I want to change my existing reservation. Can you help me in that?

ASSISTANT: Sure, I will help you. Sorry, there are no reservation found on your name.

USER: Thank you. Ok, no problem.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your information.