Hello.
Hello, how may I aid you today?
As my visa interview dates has been changed, so I would like change my existing reservation. Can you help me with it?
Sure,  I will be happy to support you. May I know your name for further proceeding?
I am Mark Thomas.
Please give me a moment, let me check your reservation and back to you.
Sure.
Unfortunately, there is no reservation found with your given name.
No problem, thank you for your assistance.
Thank you for approaching us.