You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I assist you?

USER: I am Thomas Miller. Due to sudden changes in the dates of summit which was going to held in the place.So I would like to change my existing reservation. Can you please help me in changing?

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no reservation on your name.

USER: Ok, no issue.

ASSISTANT: Thanks for choosing us.

USER: Thank you for your help.