You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Nancy Lee here.

ASSISTANT: How may I assist you?

USER: Due to heavy rain, I want to change my existing reservation. Can you please help me out?

ASSISTANT: Ok, please wait. Sorry, no reservation has been found on your name.

USER: That's ok. Thank you for your help.

ASSISTANT: Thank you for choosing us.