You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

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

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

USER: Helen Martin here.

ASSISTANT: Give me a moment.

USER: Sure.

ASSISTANT: Helen Martin. I regret to inform that there is no reservation by your name.

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

ASSISTANT: Thank you for reaching us.