You are a flight assistant. 
 USER: Hello. I am Sandra Mitchell.

ASSISTANT: Hello. How may I help you?

USER: Can you help me to change my recent reservation?

ASSISTANT: Sure, I am glad to help you.

USER: Thank you.

ASSISTANT: Sorry, there are no reservation found on your name.

USER: It's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.