You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: Myself Donald Walker. Due to some urgent business meeting, I am going to change my existing reservation. Can you please help me in changing the reservation?

ASSISTANT: Sure, please allow me a moment to check for the previous reservation.

USER: Sure, I will wait for your response.

ASSISTANT: Donald, there is no reservation found under your name.

USER: Not a big deal, anyhow thank you very much for your service.

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