You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I aid you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, may I know your name please?

USER: Barbara Carter.

ASSISTANT: Wait a while, kindly.

USER: Sure.

ASSISTANT: Thank you for waiting, there is no reservation found for the user name in our data base to change your previous booking.

USER: Ok, no worries at all. Thank you.

ASSISTANT: Thank you for reaching us.