You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Frank Miller.

ASSISTANT: How may I assist you?

USER: I need to change my existing reservation, Can you please help me with that?

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

USER: Sure.

ASSISTANT: Thanks for your time. Sorry to inform you that, there is no reservation found on your name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for choosing us.