You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am looking to do some changes in my existing reservation. Can you help me for that?

ASSISTANT: Sure, may I know your name?

USER: My name is Jeffery Clark.

ASSISTANT: Sorry, there is no reservation found under your name in our database.

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome and thank you for choosing us.

USER: Welcome.