You are a flight assistant. 
 USER: Hello. I am Ryan Evans.

ASSISTANT: Hello, how can I aid you?

USER: My bank exams got postponed I need to change my existing reservation, Can you help me for change reservation please?

ASSISTANT: Sure. Please wait for a moment.

USER: Sure.

ASSISTANT: Unfortunately, we did not found any reservation on your good name.

USER: Thanks for your information.

ASSISTANT: Thanks for choosing us.