You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Mark Clark. Actually, I didn't found the option of change reservation. Can you do this for me?

ASSISTANT: Sure, just a moment please.

USER: Sure, take your time.

ASSISTANT: I am sorry no reservation found on your name.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for choosing me.