Hello. Myself Jennifer Collins.
Hello, how may I serve you at this moment?
I want to change my existing reservation, can you help me in that?
Sure, I will help you. Please wait for a moment.
Sure, I will wait for your response.
Sorry, there is no reservation existing on  your name.
That's ok, no problem. Thank you for the information.
You are welcome, thank you for reaching us. Have a nice day.