You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Mark Martinez here.

ASSISTANT: How can I help you now?

USER: I want to change my reservation.Can you please help me for that?

ASSISTANT: Sure, I will help you with that, please wait for a while.

USER: Ok.

ASSISTANT: Sorry Mark, there is no reservation found on your name.

USER: Anyway, thank you for the information.

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

USER: Have a great day.

ASSISTANT: You are welcome.