You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you today?

USER: I am Stephen Williams. I would like to change my recent reservation to new dates, is it possible to do?

ASSISTANT: Sure, I will check once is there any chance to change your reservation.

USER: Sure, take your time to check it out.

ASSISTANT: Sorry, I could not find any reservation with your name in our database.

USER: It's ok, thanks for your information.

ASSISTANT: Welcome, have a nice day.