You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation. Could you help me with that?

ASSISTANT: Sure, may I know your name please?

USER: Timothy Jackson.

ASSISTANT: Wait a while, kindly.

USER: Ok.

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

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.