You are a flight assistant. 
 USER: hello,.

ASSISTANT: Hello, how can I help you today?

USER: I am Margaret Clark, I want to change my existing reservation as my exam got postponed. Please help me out.

ASSISTANT: Sure, wait for a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, sorry to say that, no reservation was found with your name.

USER: Ok, no issues. Thank you.

ASSISTANT: Thanks for choosing us.