You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Helen Hernandez.

ASSISTANT: How may I assist you now?

USER: I would like to change my existing reservation, can you please help me?

ASSISTANT: Helen Hernandez, please allow me to check with your booking status.

USER: Sure, take your own time.

ASSISTANT: Sorry to say, there is no flight reservation by your name.

USER: No problem, thank you for checking.

ASSISTANT: Thank you for choosing our services.