You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Christopher Smith. I need to change my existing reservation, Can you please help me that?

ASSISTANT: Sure, I am here to help you. Please stand by I will get back to you.

USER: Sure.

ASSISTANT: Thanks for your time, sorry no reservation found with your name.

USER: Ok, no problem.

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

USER: Thanks for your information.