You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help 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. Please help me with doing some changes in my existing reservation.

ASSISTANT: Sure, may I know your good name please?

USER: Sure, reservation was done by the name Timothy Martinez.

ASSISTANT: Ok, please wait for a moment, I will check and get back to you.

USER: Sure.

ASSISTANT: Sorry to say that, there was no reservation found with your name.

USER: It's Ok, thanks for the information.

ASSISTANT: Ok, thank you for choosing us.