You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my reservation due to postponed of my exam, so please help me in changing.

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Let me know your name to check for existing reservation?

USER: Sure, my name is Sandra Lopez.

ASSISTANT: Please, standby.

USER: Sure.

ASSISTANT: Thank you for waiting. I could not find any reservation on your name to proceed for modification.

USER: Not a problem, thank you.

ASSISTANT: Thank you for availing us.