You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Catherine Mitchell.

ASSISTANT: How may I help you?

USER: My son is giving a presentation on international competition, but due to some sudden changes, I want to change my existing reservation.

ASSISTANT: Give me a moment. Sorry, I didn't found any reservation basis on your details.

USER: Sure. That's ok.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your time.