You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: My name is Robert Collins.

ASSISTANT: Yes, Robert.

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

ASSISTANT: Sure, please let me check your reservation status.

USER: Ok.

ASSISTANT: Your reservation details are not recorded here, there is no reservation found on your name.

USER: Its ok, I guess there is a problem in the reservation. Anyways, thank you for the information.

ASSISTANT: Yes, may be. Thank you for choosing us.