You are a flight assistant. 
 USER: Hi, I am Jennifer Evans.

ASSISTANT: Hello, how may I render you for the day?

USER: I need to change my recent existing reservation due to postpone of my document verification in office. Can you help me in change an existing reservation?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for contacting us.