You are a flight assistant. 
 USER: Hello. I am Larry Miller.

ASSISTANT: Hello, how can I support you now?

USER: I want to modify my journey dates in existing reservation due to postpone of my trip. Assist me to modify my reservation.

ASSISTANT: Ok, then please wait. I will check your reservation for modification.

USER: Okay.

ASSISTANT: Sorry, no active reservation has been found with your name.

USER: Ok, thanks for informing.

ASSISTANT: Thanks for reaching us, have a nice day.