You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: Sure, I can help you and please allow me a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, there is no reservation found for the user name in our back end to change your booking.

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

ASSISTANT: You are most welcome and thank you for reaching us.