You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I am Joshua Collins. I want to change my existing reservation. can you help me?

ASSISTANT: Sure, I am here to help you with that. Please wait a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: Ok, thank you for the information.

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