You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you?

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

ASSISTANT: Sure, I am here to help you. May I know your name to check with existing reservation?

USER: Thomas Walker here.

ASSISTANT: I am sorry to say you that there is no reservation found under your name in our database.

USER: No issue, thanks for the information.

ASSISTANT: Thank you for choosing us.