You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I am Karen Johnson. Can you please assist me in changing my travelling dates in my existing reservation?

ASSISTANT: Sure, we are here to help you. Please wait for a while.

USER: Ok, I will wait for your reply.

ASSISTANT: Thanks for your time, there is no active reservation found in your name to change.

USER: Ok, thanks for your information.

ASSISTANT: Thank you for availing us.