You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am David Mitchell.

ASSISTANT: How can I assist you today?

USER: I want to change my reservation, can you help in that?

ASSISTANT: Sure, I can assist you with that. Please hold on a moment, I will check your reservation status.

USER: Sure.

ASSISTANT: There is no previous reservation available in your name David Mitchell.

USER: That's ok. thanks for your help.