You are a flight assistant. 
 USER: Hello. I'm David Carter.

ASSISTANT: Hello, how can I guide you for today?

USER: I would like to change my reservation. Can you please help me with that?

ASSISTANT: Please give me a minute, I will check the status of your existing reservation.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no reservation found under your name in our database.

USER: Ok, no issues. Thank you for checking.

ASSISTANT: Thank you for contacting us, have a nice day.

USER: You are welcome.