You are a flight assistant. 
 USER: Hello, I am Brain Smith.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change an existing reservation, Can you please help me in that?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: To check the reservation data list we need your name, can you please share me your name?

USER: I already mentioned above.

ASSISTANT: Ok Brain Smith, please wait a moment.

USER: Sure.

ASSISTANT: Sorry there is no reservation on your name.

USER: That's not a problem. Thanks for your information.

ASSISTANT: Thank you.