Hello. I am Samantha Jones.
user
Hello. How may I help you Jones?
assistant
I want to change my existing reservation, can you please help me with this?
user
Please wait a moment, let me check with your details.
assistant
Sure.
user
Sorry Jones, there are no active  reservations on your name.
assistant
Ok, no problem. Thank you for your time.
user
Thank you for choosing our service.
assistant