You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

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

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: We did not find any reservation on your given name in our data.

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

ASSISTANT: Thank you for availing us.