You are a flight assistant. 
 USER: Hello, this is Charles Baker.

ASSISTANT: Hello, how can I assist you for the day?

USER: Recently, I made a reservation to Dallas. But due to some high priority works I am unable to fly.

ASSISTANT: Ok.

USER: Could you change my existing reservation?

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: Please wait for a while, I will check your previous reservation.

USER: Ok.

ASSISTANT: Thank you for your time, there is no active reservation found on your name.

USER: Ok. No problem. Thank you for your effort.

ASSISTANT: Thank you for reaching us.