You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, How can I assist you today?

USER: Recently I had a reservation with the name of Richard Collins, to attend for horse racing festival. I cannot attend there due to some health issues. Can you help me to change my existing reservation?

ASSISTANT: Sure, we are happy to help you. Please wait a while.

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, not a problem. Thanks for the quick response.

ASSISTANT: Thank you for choosing us, Have a great day!.