You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donna Martinez.

ASSISTANT: How can I help you?

USER: I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Yes, I can help you. Give me a moment.

USER: Thank you, I will wait.

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

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for contacting our agency.