You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, may I know your name for checking with the previous reservation?

USER: Thank you. Dennis Young here.

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there are no active reservations on your given name to change.

USER: Not a big issue, anyhow thank you very much for checking the reservation status.

ASSISTANT: Thank you for reaching our service.