You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I have to change my reservation due to my planned event got postponed. So please help me with that.

ASSISTANT: Sure, may I know your name to check your reservation from our database?

USER: Thank you. Please check the reservation with my name Helen Lewis.

ASSISTANT: We regret to inform you that there is no active reservation found on your name to change.

USER: Oh! It may not be booked properly. Anyway, thank you for time.

ASSISTANT: Thank you for opting us.

USER: Most welcome.