You are a flight assistant. 
 USER: Hello, I am Kevin Williams.

ASSISTANT: Hello, Kevin Williams, How can I help you the best today?

USER: Could you please help me to change an existing reservation as my trip got postpone due to my leaves are not approved?

ASSISTANT: Sure, I can help you to change your reservation.

USER: Thank you.

ASSISTANT: Please let me allow, to check your reservation status.

USER: Sure.

ASSISTANT: Thanks for your time, there is no active reservation on you rname to change it.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thanks for your presence.