You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: I have postponed my trip due to some health issue, so please help me to change my existing reservation.

ASSISTANT: Sure, can i know your name?

USER: My name is Larry Williams.

ASSISTANT: I'm sorry Larry, there are no reservations with your name.

USER: Ok, no problem.

ASSISTANT: Thank you, have a good day.

USER: Thank you for searching.