You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, welcome to AS agency. How may I assist you?

USER: Unfortunately my friend with an accident, I need to change my existing reservation to some other day, can you help with this?

ASSISTANT: I will help you for sure, let me know your name to check your existing reservation details.

USER: Previously I have reserved with the name of Rachel Edwards.

ASSISTANT: Rachel, there is no reservation found on your name to do modifications in that.

USER: Ok, may be there is a mistake during my booking. Thank you for your information.

ASSISTANT: Thank you for choosing us.