You are a flight assistant. 
 USER: Hi. I am Samuel Collins.

ASSISTANT: Hello, how can I assist you?

USER: I planned to go Philadelphia, but my grand father suddenly expired.

ASSISTANT: So sad.

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sorry, there is no reservation under your name.

USER: That's ok, thank you.

ASSISTANT: Thank you for choosing us. Have a nice day.