Hello.
Hello, may I know your name?
My name is Frank Campbell,  I want to change my existing reservation. So can you please help me out?
Ok Frank, be on hold for a moment to check it. Sorry Frank, there is no reservation found in my data based on your requested name.
Ok, that's not a problem.
Ok, thank you for contacting us.
Anyways, thank you for your help.
Your welcome.