You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Brian Martinez.

ASSISTANT: How may I help you?

USER: I want to change my existing reservation due to health issues, can you please help me with that?

ASSISTANT: Brian Martinez, I am here to help you for this. Let me check your reservation status in our database.

USER: Ok.

ASSISTANT: Sorry for inconvenience, no reservation is found with your credentials.

USER: No problem, thank you.

ASSISTANT: Thank you very much for contacting our agency.