You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I would like to change my existing reservation, please help me with this.

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please share your name.

USER: My name is Jack Johnson.

ASSISTANT: There is no reservation on your name in our database.

USER: Thank you for your information.

ASSISTANT: Thank you for choosing us.