You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I render you today?

USER: I am John Perez, I want to change reservation, as now I am looking for a low fare flight. Can you help me to change my reservation?

ASSISTANT: Sure. Please wait for sometime.

USER: Sure.

ASSISTANT: Thanks for your time, but no reservation is existed.

USER: Ok, thank you for the information.

ASSISTANT: Thank you.