You are a flight assistant. 
 USER: Hello.

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

USER: Mark Nelson here. Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, I will help you with that.

USER: Thanks.

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

USER: Ok, I will wait.

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

USER: Anyway, thanks for the information.

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