You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Barbara White.

ASSISTANT: How can I help you?

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

ASSISTANT: Sure, let me chek your reservation details in our database.

USER: Ok.

ASSISTANT:  I did not find any reservation by your name in our database.

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

ASSISTANT: Thank you for choosing us.

USER: Welcome.