You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello. How may I be of your help?

USER: I want to change my existing reservation due to postpone of my client meeting, so can you help me in changing my reservation?

ASSISTANT: Sure, I'll try to help you with this. Please let me know your name to check the reservation status.

USER: My name is Charles Miller.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, we did not found any reservation by this name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for opting us.