Hello.
user
Hello, how may I serve you?
assistant
I want to change my existing reservation. Could you help me with that?
user
Sure, I will help you. Please send your travelling dates.
assistant
Please check with this name Karen Thomas for my previous reservation.
user
Sure. Sorry, there is no reservation available with your given name.
assistant
That's ok, thank you.
user
You are welcome, have a nice day.
assistant