Hello. Jack Walker here.
Hello Jack. How can I help you today?
I want to make some changes in my existing reservation because I did not get the concert tickets, so planning to travel on another date, can you please help me?
Sure, I will help you Jack. Please give me a moment.
Ok.
No previous reservation available in our data on your name  Jack Walker.
It's ok, no problem. Thank you for checking.
Thank you for reaching us, have a nice day.