You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I want to change my reservation with new dates, can you help me with that?

ASSISTANT: Sure, I'll help you in changing an existing reservation. Could you please let me know your name to check the reservation status?

USER: My name is Brian Thompson.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry, there is no active reservation have been found under your name in our database to amend it.

USER: Thank you for helping me.

ASSISTANT: Thank you for choosing us.