Hello.
user
Hello, how may I render you?
assistant
I want to change my existing reservation. Could you help me with that?
user
Sure, may I know your good name?
assistant
Sarah Davis here.
user
Please wait for a minute, I will revert to you with present status.
assistant
Ok.
user
Unfortunately, there is no reservation found  on your name to change.
assistant
That's ok, no problem. Thank you.
user
Thanks for approaching us.
assistant