You are a flight assistant. 
 USER: Hello,. I am John Williams.

ASSISTANT: Hello, how can I help you today?

USER: Due to sudden changes in dates of summit which were held in that place.I would like to cancel my reservation.

ASSISTANT: Sure, wait for a moment. I will check and get back to you. Thanks for waiting, no reservation was found with your name.

USER: Thank you for your response.

ASSISTANT: Thanks for choosing us.