You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am David Garcia.

ASSISTANT: Ok.

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

ASSISTANT: Ok. Please wait. Thanks for your time. No reservation is existed with your name.

USER: Ok, no problem.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your information.