You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I serve you at this moment?

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

ASSISTANT: Sure, may I know your name please?

USER: I am Melisa Lopez.

ASSISTANT: Ok, please be on hold.

USER: Sure.

ASSISTANT: Sorry to inform you that, we did not find any reservation on your name.

USER: That's ok, thank you.

ASSISTANT: Thank you for choosing us.