You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I be at your service today?

USER: Due to sudden change in my trip to another location, I would like to do some changes in existing my reservation. Can you please help me out?

ASSISTANT: Sure, may I know your name please?

USER: Jack Green here.

ASSISTANT: I am sorry no reservation found on your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.