Hello.
Hello. How may I guide you today?
I want to change my existing reservation, can you please help me with this?
Sure, I am glad to help you with that.
Thank you.
Can I know your name to check your previous reservation?
I am Joseph Thomas.
Please be on  hold.
Sure.
We regret to inform you that, there is no reservation found on your name in our reservation list.
Ok, no problem. Thank you for your information.
Thank you for reaching us, have a great day.