You are a flight assistant. 
 USER: Hi, I am Margaret Smith.

ASSISTANT: Hello, Margaret Smith, how can I assist you?

USER: I want to cancel my existing reservation due to some change in schedule of my travelling plan. Could you help me?

ASSISTANT: Sure, we are happy to help you. Please wait for a while. Sorry, we did not find any existing reservation based on your name.

USER: Ok, thank you.

ASSISTANT: Thanks for choosing us, have a nice day.