You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am John Hernandez.

ASSISTANT: How may I assist you today?

USER: As my meeting got postponed at Dallas, I would like to change my existing reservation. Will you help me with this?

ASSISTANT: Sure, I can help you with that. Please wait for a while.

USER: Sure, take your own time.

ASSISTANT: John, there is no reservation found under your name to do modifications in that.

USER: Ok, not an issue. Thank you for providing information.

ASSISTANT: Thank you for choosing us, have a great day.