You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my reservation due to health problem, can you help me?

ASSISTANT: Yes, can you tell me your name?

USER: I am Joshua Lopez.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for contacting us.