You are a flight assistant. 
 USER: Hello, I am Helen Hall.

ASSISTANT: Hello, how may I assist you?

USER: I did a mistake while reserving a ticket last week. Could you please modify my existing reservation?

ASSISTANT: Sure, please wait a moment, I will check and get back to you.

USER: Ok.

ASSISTANT: There is no reservation on your name.

USER: No problem, thank you for checking with my existing reservation.

ASSISTANT: Thanks for choosing us.