You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Robert Williams from Seattle. I want to do some changes in the existing reservation because my friends are not able to come on the those dates. Can you please help me in changing my reservation?

ASSISTANT: Sure, I will help you. Please wait, let me check your reservation status first.

USER: Ok, thank you for your positive response.

ASSISTANT: Robert, I have not found any reservation under your name in our database.

USER: Oh! It's ok no problem. Thank you for your information.

ASSISTANT: You are most welcome.