You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Barbara Perez.

ASSISTANT: How may I help you?

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

ASSISTANT: Wait a minute.

USER: Sure.

ASSISTANT: Sorry, there was no reservation on your name.

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

ASSISTANT: Thank you.