You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: I need to change my existing reservation, can you please help me with that?

ASSISTANT: Sure. May I know your name please?

USER: Frank Walker here.

ASSISTANT: I will have to check for the flight reservation. Wait for a moment please.

USER: Sure.

ASSISTANT: Sorry I could not find your flight reservation to change it.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Thanks for your information.