You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I help you?

USER: I am Margaret Lee. Due to my sports event has been preponed, I would like to change my existing reservation. Can you please help me with that?

ASSISTANT: Sure, please stand by I will revert you.

USER: Ok.

ASSISTANT: Thank you, sorry no reservation found with your name.

USER: Thank you for your kind service.

ASSISTANT: Have a nice day.