You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you at this moment?

USER: I am Anna Williams.

ASSISTANT: Yes Anna.

USER: Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I will change your reservation, please wait for a moment to check your reservation status.

USER: Sure, I will wait.

ASSISTANT: Anna, there is no any active reservation with your name in my database.

USER: That's fine.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your service.