You are a flight assistant. 
 USER: Hi. Christine Young here.

ASSISTANT: Hello, how may I assist you?

USER: Please change my existing reservation to new dates.

ASSISTANT: Sure, I am here to help.

USER: Thank you.

ASSISTANT: Please, let me check the previous reservation details on your name.

USER: Sure.

ASSISTANT: Sorry Young, no reservation found on your name in our data base.

USER: It's ok, thanks for checking.

ASSISTANT: Thank you for reaching us.