You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, May I know your good name?

USER: My name is Benjamin Nelson.

ASSISTANT: How can I serve you?

USER: I want to change my existing reservation due to some problem,will you help me?

ASSISTANT: Sure. Please wait a moment I will check the reservation with your name.

USER: OK.

ASSISTANT: We do not found reservation with your name.

USER: OK,not an issue. Thank you for your service.

ASSISTANT: Thank you for contacting us.