You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Donald Brown.

ASSISTANT: How may I help you out?

USER: I would like to change my existing reservation to some other dates. Can you help me?

ASSISTANT: Sure, I will help you in changing the reservation. Sorry, there are no reservations found in our database.

USER: Its ok, no issues. Thank you for the information.

ASSISTANT: Thank you for choosing us.