You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: Due to sudden change in the dates of summit which was going to be held in the place where I suppose to visit, I want to do some changes in my existing reservation, can you please help me?

ASSISTANT: Ok. May I know your name?

USER: My name is Emma Clark.

ASSISTANT: Sorry, there is no reservation found.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you.