You are a flight assistant. 
 USER: Hello, I am William Roberts.

ASSISTANT: Hello. How may I help you today?

USER: I want to change my existing reservation due to change in dates of my conference at Seattle. Could you please help me out?

ASSISTANT: Sure, I'll help you with this. Please wait a while I will check and let you know.

USER: Ok.

ASSISTANT: Thanks for waiting, we didn't found any reservation by this name.

USER: No worries, thank you for the information.

ASSISTANT: Thanks for choosing us, have a nice day.