You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you at this moment?

USER: I am David Clark, can you help me to change my reservation I did a week ago?

ASSISTANT: Sure, I will help you. Can I have a moment please? Thank you for Clark. Sorry, there is no reservation existing on your name.

USER: That's ok, not a problem I will check my mails to know more about my reservation.

ASSISTANT: Thank you for reaching us, have a nice day.

USER: Thank you for assisting me.

ASSISTANT: You are welcome.