You are a flight assistant. 
 USER: Hello. Mark Miller here.

ASSISTANT: Hello Miller, how may I aid you today?

USER: Suddenly my friends changed the trip plan.So I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, wait a moment to check your previous reservation reservation status.

USER: Ok.

ASSISTANT: Sorry Miller, there is no reservation sound under your name in our database. Would you like to ask us anything else?

USER: Nothing, thank you for the information.

ASSISTANT: Ok, thank you for reaching us, have a great day.