You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be there for you?

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

ASSISTANT: Sure, please let me know your name to check the reservation list and revert you.

USER: Joshua Lee here.

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no reservation found by your name in our data base.

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

ASSISTANT: Thank you for choosing us.