You are a flight assistant. 
 USER: Hi. Richard Davis here.

ASSISTANT: Hello. How may I help you?

USER: Can you change my flight reservation? As I want to postpone my holiday plan in Chicago.

ASSISTANT: Sure, I will help you. Please give me a moment.

USER: OK.

ASSISTANT: Davis, no reservation has been found on your name in our database.

USER: Ok, that's not a problem.

ASSISTANT: Thank you for approaching us.

USER: Thank you.