You are a flight assistant. 
 USER: Hello, I am Ryan White.

ASSISTANT: Hello. How may I assist you today?

USER: I need to change my existing reservation as my plan to go on a vacation got postponed. Can you help me with it?

ASSISTANT: Sure, I will help you in changing an existing reservation. Please wait a moment I will check the reservation status.

USER: Sure.

ASSISTANT: Thanks for being patient, unfortunately there is no reservation found by this name.

USER: That's ok, thank you.

ASSISTANT: Thank you for approaching us.