You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Elizabeth Campbell.

ASSISTANT: How can I assist you at this moment?

USER: Can you help me for changing my existing reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Ok, please wait a moment.

USER: OK.

ASSISTANT: Sorry Elizabeth Campbell, no reservation has found under your name to change.

USER: Oh! It's ok no problem, thank you for your services.

ASSISTANT: Thank you for choosing us, have a good day.