You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. May I know how best I can help you today?

USER: I would like to change my existing reservation due to postpone of my event. Could you please help me?

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

USER: I am Alexander Walker.

ASSISTANT: Thank you for providing your name, please wait for some time.

USER: Sure.

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

USER: No worries, thank you for the information.

ASSISTANT: Thank you for availing us.