You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation, due to some health issue. Can you help me?

ASSISTANT: Sure, may I know your name please?

USER: Ok, I am Benjamin Smith.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, not a problem. Thank you for your help.

ASSISTANT: Thank you for opting us.