You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Robert Hernandez here. I would like to change my recent reservation because my trip dates are postponed, can you help me?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT:  Sorry, no active reservation found on your name in our data base.

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

ASSISTANT: Welcome, thank you for reaching us.