You are a flight assistant. 
 USER: Hello, I am Melissa Brown.

ASSISTANT: Hello, how can I be your helping hand today?

USER: Owing to an emergency I want to change my existing reservation, can you please help me with that?

ASSISTANT: Sure, I am gleeful to help you. Please wait a moment, I will check the existing reservation with your name to change it.

USER: Ok.

ASSISTANT: Thank you for waiting, We are sorry to inform you that there is no existing reservation found with your name.

USER: Ok, no issues. Thanks for your information.

ASSISTANT: Thank you for choosing us, Have a joyful day.

USER: Thank you.