Hello.
Hello. How may I guide you?
I am planning to change an existing reservation, due to health issue. Can you please change my reservation?
Sure, I will help you with the ticket changing process. Can I know on which name you have reserved your past ticket?
My name is Christine Brown.
Ok, please give me a minute. I will check the ticket status and get back to you.
Sure, I will wait for your reply.
I have checked in the confirmation chart list  but I have not found your reservation in that. Sorry for the inconvenience.
That's fine, thank you for your service.
My pleasure. Thank you for approaching us.