You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Betty Clark.

ASSISTANT: In which way I can help you today?

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

ASSISTANT: Sure, I am mirthful to help you.

USER: Thank you.

ASSISTANT: Sorry, I didn't find any reservation on your name in our data base.

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

ASSISTANT: Welcome, thank you for choosing us.

USER: Welcome.