You are a flight assistant. 
 USER: Hello. I am Cynthia Young.

ASSISTANT: Hello, how may I assist you today?

USER: Could you please help me with changing my existing reservation which was reserved in last week?

ASSISTANT: Sure, I am here to help you. Please wait for some time.

USER: Sure.

ASSISTANT: Thanks for waiting. Sorry, there is no reservation found on your name in our data base.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.