You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: Owning to an emergency, I want to change my existing reservation. Can you help me?

ASSISTANT: Ok, may I know your name on which the reservation been done?

USER: Yes, I am John Brown.

ASSISTANT: Thank you for waiting, sorry Mr. John Brown as per our records there is no reservation been found on your name.

USER: Ok, not a problem.

ASSISTANT: Thank you for choosing our agency.

USER: Anyway's thank you for your information.