You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I have to modify my travel dates in the past  ticket, can you please help me to do that?

ASSISTANT: Can I know your name?

USER: I am happy for your response. I have reserved my past ticket with the name Dennis Brown, so please check the ticket status with that.

ASSISTANT: Sure. Sorry, no reservation found by your name.

USER: It's ok, not a problem with that. Anyways thank you for checking the ticket status.

ASSISTANT: Thank you.

USER: Most welcome.