Hello, I am Robert Williams.
Hello, How may I amend you?
 I made a reservation earlier to go for a holiday trip with my friends, due to some financial problems I want to change my existing reservation. Can you help me in changing reservation?
Sure, I will help you out.
Ok.
Please wait for a while, I will revert to you.
Sure.
No reservation is done earlier on your name to proceed further.
Ok, No issues.
Thank you for availing us, Have a great day.