You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: Actually I have planned to travel to Atlanta, but due to some reasons the travel dates has been changed, so I need to change my reservation. Can you help me out?

ASSISTANT: Sure, can I know your name for checking the details?

USER: Sure, my existing ticket is with name Margaret Allen.

ASSISTANT: Hold on for a minute. I will be back with the details. Sorry to say Allen, I couldn't find any reservation on your  name.

USER: It's ok, thank you for searching.

ASSISTANT: You are welcome.