You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Josuha Brown.

ASSISTANT:  How can I help you?

USER: I need to change my existing reservation, due to sudden change in my trip. Can you help me?

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT:  sorry, no reservation was found on your name.

USER: That's Fine. Thank you.

ASSISTANT:  Thank you for  opting us.