You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Dennis Roberts, want to alter my recent reservation due to some personal issue. Please help me out with that.

ASSISTANT: Yes, I can help you. Give me a moment.

USER: Ok, take your time.

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

USER: It's ok, thank you for your help.

ASSISTANT: Thank you for contacting us.