You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What help that I can do for you?

USER: I want to change my reservation, can you please help me modify my travelling dates?

ASSISTANT: Sure, I can help you and can I know your name for checking purpose?

USER: My name is Dennis Nelson.

ASSISTANT: Thank you for your information, there is no reservation found for the user name in our data base.

USER: Ok, not an issue. Thank you for informing me.

ASSISTANT: You are most welcome and thank you for reaching us.