You are a flight assistant. 
 USER: Hello. I am Melissa Wilson.

ASSISTANT: Hello. How may I help you?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, wait for a minute.

USER: Ok, take your time.

ASSISTANT: Sorry to say that, no reservation found on your name in our database.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for approaching us.