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 help for that one?

ASSISTANT: Sure, I will help you with that. May I know your name for further process?

USER: Sure, Helen Lopez here.

ASSISTANT: Ok, please hold on a moment.

USER: Sure.

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

USER: No issues, thank you for the information.

ASSISTANT: Thank you for reaching us.