You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

USER: I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure, I will help you with the ticket changing process. Can I know on which name you have reserved your past ticket?

USER: My name is Christine Brown.

ASSISTANT: Ok, please give me a minute. I will check the ticket status and get back to you.

USER: Sure, I will wait for your reply.

ASSISTANT: I have checked in the confirmation chart list  but I have not found your reservation in that. Sorry for the inconvenience.

USER: That's fine, thank you for your service.

ASSISTANT: My pleasure. Thank you for approaching us.