You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I am Joshua Johnson, can you help me for changing my existing reservation?

ASSISTANT: Yes, I can help you.

USER: Thank you.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Oh! It's ok no problem.

ASSISTANT: Thank you for consulting us.

USER: Thank you for your services.