You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Raymond Williams here.

ASSISTANT: How may I guide you today?

USER:  I would like to spend some more days with my family, so please help me in changing my existing reservation.

ASSISTANT: Sure, I will help you with that. Please wait for a while.

USER: Ok.

ASSISTANT: Hall, I am sorry to say that there is no reservation found.

USER: That's ok, thank you for your help.

ASSISTANT: Thank you for reaching us.