You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, we are here to help you. May I know your name please?

USER: Thank you. Mary Campbell here.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: No issues, thank you.

ASSISTANT: Thank you for contacting us.