You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you at this moment?

USER: David White here.

ASSISTANT: Yes White.

USER: Due to sudden change in my concert dates, I want to change my reservation. Can you help me?

ASSISTANT: Ok. Sure, I will help you.

USER: Fine.

ASSISTANT: David, I did not find any reservation with your name.

USER: It's ok.

ASSISTANT: Anything else to help you.

USER: Thank you for your immediate response. No thanks.

ASSISTANT: Thank you for reaching us. Have a nice day.

USER: You are welcome.