Hello.
user
Hello. How can I assist you today?
assistant
I am Mark Brown. Due to my health problem I want to change my reservation, can you please help me to change my reservation?
user
Sure, please allow me a moment to check for the previous reservation.
assistant
Sure, I will wait.
user
Mark, there is no reservation found under your name.
assistant
That's fine. Thank you for  your service.
user
Thank you for reaching us.
assistant