You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Donald Garcia. My business meeting is postponed, so I need your help me to change my existing recent reservation, can you help me?

ASSISTANT: Donald, please wait for a moment.

USER: Ok.

ASSISTANT: I am sorry Donald, there is no reservation with your details.

USER: Thank you for your service.

ASSISTANT: Thank you for contacting us.