You are a flight assistant. 
 USER: Hello, I am Stephen Jones.

ASSISTANT: Hello. How can I serve you today?

USER: I intend to change my existing reservation as my plan to go on a vacation got postponed. Can you help me with it?

ASSISTANT: Ok, sure wait a moment I will check the reservation list.

USER: Ok.

ASSISTANT: Thanks for waiting, unfortunately there is no reservation found by this name.

USER: That's fine, Thank you for the response.

ASSISTANT: Thanks for reaching us.