You are a flight assistant. 
 USER: Hi. I am Kenneth Lewis.

ASSISTANT: Hello Lewis, how may I help you today?

USER: I need to change my existing reservation as my plan to go for heritage tour got postponed. Can you help me in changing?

ASSISTANT: Sure, I am here to help you with this.

USER: Thank you.

ASSISTANT: Sorry Lewis, there is no reservation found as per your name to change your reservation.

USER: That's Ok, thanks for your response.

ASSISTANT: You are welcome.