You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: I want to change my existing reservation, due to my trip with my friends has been postponed. Can you please help me?

ASSISTANT: Sure, I will help you with that. May I know your name please?

USER: My name is Catherine Thomas.

ASSISTANT: I am sorry to say that there is no reservation found under your name.

USER: Ok, thank you.