You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: William Mitchell here.

ASSISTANT: How can I aid you?

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

ASSISTANT: Sure, I will help you with that.

USER: Thank you for responding.

ASSISTANT: William Mitchell, there are no flights available in your route.

USER: That's ok, no problem. Thank you for checking out.

ASSISTANT: Thank you for approaching us.