You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Joseph Jackson. I want to change my existing reservation due to heavy rainfall, can you help me in change reservation?

ASSISTANT: Sure, we are here to help you. Please wait a moment, I will check your details and get back to you with the status.

USER: Sure.

ASSISTANT: Unfortunately, there is no reservation exist on the name Joseph Jackson to do modification.

USER: No problem, thank you.

ASSISTANT: Thank you for consulting us.