You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you at this moment?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I will help you with that. Can you please mention your name for further process?

USER: William Jackson.

ASSISTANT: Ok, please hold on a moment.

USER: Ok.

ASSISTANT: There is no previous reservation available under your name.

USER: It's ok, thank you.

ASSISTANT: Thank you for reaching us.