You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am John Thomas. I want to change my existing reservation. Could you help me in that?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please wait.

USER: Ok.

ASSISTANT: Thanks for waiting. There is no reservation on your name.

USER: That's ok. Thank you.

ASSISTANT: Thank you.