You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I am Linda Allen. I would like to spend some more days with my friend's, so please help me in changing my existing reservation?

ASSISTANT: Please wait for a moment.

USER: Sure, take your own time.

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

USER: That's really sad. Thank you for your service.

ASSISTANT: Thank you for choosing us.

USER: Welcome.