You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you today?

USER: I want to change my existing reservation due to some health issue. Can you help me in that?

ASSISTANT: Sure, Let me know your name to check your reservation?

USER: Richard Martin.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for choosing us.