You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Sure, please share your name and let me see if I can help you with it.

USER: Sure, I am Richard Moore.

ASSISTANT: Can you please wait for a while?

USER: Sure.

ASSISTANT: I am sorry to inform you that I cannot see your reservation in our list.

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

ASSISTANT: Thank you for reaching us.