You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you?

USER: I want to change my existing reservation due to sudden change in the journey plan.

ASSISTANT: Sure, we will help you.

USER: Thank you.

ASSISTANT: May I know your name to check our reservation list?

USER: Dennis Davis here.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: I regret, there is no reservation found on the name Dennis Davis.

USER: Ok, not a problem.

ASSISTANT: Thank you for opting us.

USER: Thank you for your help.