You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Sandra Edwards.

ASSISTANT: How may I guide you?

USER: I would like to change my existing reservation to some other dates. Can you help me?

ASSISTANT: Sure, I will help you. Please wait a moment.

USER: Sure.

ASSISTANT: Sandra, no reservation has been found on your name in our database.

USER: Its ok, thank you for the information.

ASSISTANT: Thank you for choosing us.