You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, can you please provide me your name?

USER: Melissa Miller.

ASSISTANT: Give me a moment.

USER: Sure.

ASSISTANT: Melissa Miller. I regret to inform that there is no reservation by your name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.