You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I help you today?

USER: I need to change my existing reservation due to an emergency.

ASSISTANT: Sure, I will help you with that. May I know your good name?

USER: My name is Donald Carter.

ASSISTANT: Please wait for while, I check for reservation.

USER: Ok.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name.

USER: Thanks.

ASSISTANT: Thank you for reaching us.