You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Richard Thomas.

ASSISTANT: How may I help you?

USER: Due to some change in the plan, I would like to change my existing reservation. Can you help me?

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: Richard, no reservation has been found on your name.

USER: Anyways, thank you for the information. Its ok, I guess there is a problem occurred while booking.

ASSISTANT: Thank you for choosing us.