You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am David Hernandez.

ASSISTANT: How can I assist you today?

USER: I need to change my existing reservation as my exams got postponed, Can you please help me with that?

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Unfortunately we did not find any reservation on your given name in our data.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for opting us.